Cross linked surface coating and interfacial layer for a perovskite material photovoltaic device

ABSTRACT

A photovoltaic device includes a photoactive material comprising a perovskite material and an interfacial layer comprising a cross-linked polymer that comprises a fullerene or fullerene derivative, a cross-linking agent, and one or more polymers selected from the group consisting of polystyrene, [6,6]-phenyl-C61-butyric acid methyl ester, poly(4-vinylphenol), [6,6]-phenyl-C61-butyric acid, and any combination thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/941,320 filed Nov. 27, 2019 and entitled “CROSS LINKED SURFACECOATING AND INTERFACIAL LAYER FOR A PEROVSKITE MATERIAL PHOTOVOLTAICDEVICE,” the contents of which are incorporated by reference herein inits entirety.

BACKGROUND

Use of photovoltaics (PVs) to generate electrical power from solarenergy or radiation may provide many benefits, including, for example, apower source, low or zero emissions, power production independent of thepower grid, durable physical structures (no moving parts), stable andreliable systems, modular construction, relatively quick installation,safe manufacture and use, and good public opinion and acceptance of use.

PVs may incorporate layers of perovskite materials as photoactive layersthat generate electric power when exposed to light. Additional layers inPV devices may assist transport of charge from the photoactive layer.Selection of charge transporting layers may affect PV device performanceand durability.

The features and advantages of the present disclosure will be readilyapparent to those skilled in the art. While numerous changes may be madeby those skilled in the art, such changes are within the spirit of theinvention.

SUMMARY

According to some embodiments, a method for producing a perovskitematerial photovoltaic device includes depositing a perovskite material,depositing a layer of fullerenes, depositing a halosilylalkane, andheating the alkyl hydroxide to cause the halosilylalkane to bind to thefullerenes.

According to some embodiments, a cross-linked polymer includes ahalosilylalkane and one or more monomers selected from the groupconsisting of polystyrene, [6,6]-phenyl-C61-butyric acid methyl ester,poly(4-vinylphenol), [6,6]-phenyl-C61-butyric acid, and combinationsthereof.

According to some embodiments, a photovoltaic device includes aphotoactive material comprising a perovskite material. The photovoltaicdevice also includes an interfacial layer comprising a cross-linkedpolymer that comprises a halosilylalkane and one or more monomersselected from the group consisting of polystyrene,[6,6]-phenyl-C61-butyric acid methyl ester, poly(4-vinylphenol),[6,6]-phenyl-C61-butyric acid, and combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a typical photovoltaic (PV) cell includingan active layer, according to some embodiments of the presentdisclosure.

FIG. 2 is a stylized diagram showing components of an example PV device,according to some embodiments of the present disclosure.

FIG. 3 is a stylized diagram showing components of an example device,according to some embodiments of the present disclosure.

FIG. 4 is a stylized diagram showing components of an example device,according to some embodiments of the present disclosure.

FIG. 5 is a stylized diagram showing an illustration of aRuddlesden-Popper perovskite.

FIG. 6 is a stylized diagram showing an illustration of a perovskitematerial with addition of an alkyl ammonium cation, according to someembodiments of the present disclosure.

FIG. 7 is a stylized diagram showing an illustration of a perovskitematerial with a 1-butylammonium surface layer, according to someembodiments of the present disclosure.

FIG. 8 is a stylized diagram showing an illustration of a perovskitematerial with a surface layer of multiple bulky organic cations,according to some embodiments of the present disclosure.

FIG. 8A is a stylized diagram showing an illustration of a perovskitematerial with a surface layer of multiple bulky organic cations,according to some embodiments of the present disclosure.

FIG. 9 is an illustration of a comparison of images taken of aperovskite material with and without a 1-butylammonium (“BAI”) surfacecoating, according to some embodiments of the present disclosure.

FIG. 10 is a stylized diagram showing an illustration of a comparison ofimages taken of a perovskite material with and without a 1-butylammonium(“BAI”) surface coating, according to some embodiments of the presentdisclosure.

FIGS. 11A-D illustrate various perylene monoimides and diimides that maybe applied to the surface of a perovskite material, according to someembodiments of the present disclosure.

FIG. 12 is a stylized diagram showing an illustration of a perovskitematerial with addition of a perylene monoimides ammonium cation,according to some embodiments of the present disclosure.

FIG. 13 is a stylized diagram showing an illustration of 1,4-diammoniumbutane incorporated into the crystal lattice of a formamidinium leadiodide perovskite material, according to some embodiments of the presentdisclosure.

FIG. 14 is an illustration of x-ray diffraction peaks (XRD) forperovskite having various concentrations of 1,4-diammonium butane,according to some embodiments of the present disclosure.

FIG. 15 provides images of perovskite material samples having variousconcentrations of 1,4-diammonium butane over time, according to someembodiments of the present disclosure.

FIG. 16 provides illustrations of poly-ammonium alkyl cations, accordingto some embodiments of the present disclosure.

FIG. 16A is a stylized diagram showing an illustration of 1,8 diammoniumoctane incorporated into the crystal lattice of a formamidinium leadiodide perovskite material, according to some embodiments of the presentdisclosure.

FIG. 16B is a stylized diagram showing an illustration ofbis(4-aminobutyl)-ammonium incorporated into the crystal lattice of aformamidinium lead iodide perovskite material, according to someembodiments of the present disclosure.

FIG. 16C is a stylized diagram showing an illustration oftris(4-aminobutyl)-ammonium incorporated into the crystal lattice of aformamidinium lead iodide perovskite material, according to someembodiments of the present disclosure.

FIGS. 17-28 provide illustrations of the structures of certain organicmolecules, according to some embodiments of the present disclosure.

FIG. 29 illustrates x-ray diffraction patterns of perovskites materials,according to some embodiments of the present disclosure.

FIG. 30 provides a stylized illustration of thicknesses of inorganicmetal halide sublattices of perovskite materials, according to someembodiments of the present disclosure.

FIG. 31 shows optical and photoluminescence images of perovskitematerial photovoltaic devices according to some embodiments of thepresent disclosure.

FIG. 32 illustrates power output curves of perovskite materialphotovoltaic devices, according to some embodiments of the presentdisclosure.

FIG. 33 illustrates current-voltage (I-V) scans of perovskite materialphotovoltaic devices, according to some embodiments of the presentdisclosure.

FIG. 34 illustrates box plots for open-circuit voltage (Voc),short-circuit current density (Jsc), Fill Factor (FF) and powerconversion efficiency (PCE) for perovskite material photovoltaicdevices, according to some embodiments of the present disclosure.

FIG. 35 illustrates external quantum efficiency (EQE) curves ofperovskite material photovoltaic devices, according to some embodimentsof the present disclosure.

FIG. 36 shows admittance spectroscopy plots of perovskite materialphotovoltaic devices, according to some embodiments of the presentdisclosure.

FIG. 37 illustrates a structure of a crosslinked interfacial layer,according to certain embodiments.

FIG. 38 illustrates a structure of a crosslinked interfacial layer,according to certain embodiments.

FIG. 39 illustrates a structure of a crosslinked interfacial layer,according to certain embodiments.

FIG. 40 illustrates a structure of a crosslinked interfacial layer,according to certain embodiments.

FIG. 41 illustrates a structure of a crosslinked interfacial layer,according to certain embodiments.

FIG. 42 illustrates a structure of a crosslinked interfacial layer,according to certain embodiments.

FIG. 43 illustrates a structure of a crosslinked interfacial layer,according to certain embodiments.

FIG. 44 illustrates a structure of a crosslinked interfacial layer,according to certain embodiments.

FIG. 45 illustrates a structure of a crosslinked interfacial layer,according to certain embodiments.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Improvements in various aspects of PV technologies compatible withorganic, non-organic, and/or hybrid PVs promise to further lower thecost of both organic PVs and other PVs. For example, some solar cells,such as perovskite PV solar cells, may take advantage of novelcost-effective and high-stability alternative components, such as nickeloxide interfacial layers. In addition, various kinds of solar cells mayadvantageously include chemical additives and other materials that may,among other advantages, be more cost-effective and durable thanconventional options currently in existence.

The present disclosure relates generally to compositions of matter,apparatus and methods of use of materials in photovoltaic cells increating electrical energy from solar radiation. More specifically, thisdisclosure relates to photoactive and other compositions of matter, aswell as apparatus, methods of use, and formation of such compositions ofmatter.

Some or all of materials in accordance with some embodiments of thepresent disclosure may also advantageously be used in any organic orother electronic device, with some examples including, but not limitedto: batteries, field-effect transistors (FETs), light-emitting diodes(LEDs), non-linear optical devices, memristors, capacitors, rectifiers,and/or rectifying antennas.

In some embodiments, the present disclosure may provide PV and othersimilar devices (e.g., batteries, hybrid PV batteries, multi-junctionPVs, FETs, LEDs, x-ray detectors, gamma ray detectors, photodiodes,CCDs, etc.). Such devices may in some embodiments include improvedactive material, interfacial layers (IFLs), and/or one or moreperovskite materials. A perovskite material may be incorporated intovarious of one or more aspects of a PV or other device. A perovskitematerial according to some embodiments may be of the general formulaCMX₃, where: C comprises one or more cations (e.g., an amine, ammonium,phosphonium, a Group 1 metal, a Group 2 metal, and/or other cations orcation-like compounds); M comprises one or more metals (examplesincluding Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge,Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr); and X comprises one ormore anions. Perovskite materials according to various embodiments arediscussed in greater detail below.

Photovoltaic Cells and Other Electronic Devices

Some PV embodiments may be described by reference to the illustrativedepictions of solar cells as shown in FIG. 1. An example PV architectureaccording to some embodiments may be substantially of the formsubstrate-anode-IFL-active layer-IFL-cathode. The active layer of someembodiments may be photoactive, and/or it may include photoactivematerial. Other layers and materials may be utilized in the cell as isknown in the art. Furthermore, it should be noted that the use of theterm “active layer” is in no way meant to restrict or otherwise define,explicitly or implicitly, the properties of any other layer—forinstance, in some embodiments, either or both IFLs may also be activeinsofar as they may be semiconducting. In particular, referring to FIG.1, a stylized generic PV cell 1000 is depicted, illustrating the highlyinterfacial nature of some layers within the PV. The PV 1000 representsa generic architecture applicable to several PV devices, such asperovskite material PV embodiments. The PV cell 1000 includes atransparent substrate layer 1010, which may be glass (or a materialsimilarly transparent to solar radiation) which allows solar radiationto transmit through the layer. The transparent layer of some embodimentsmay also be referred to as a superstrate or substrate (e.g., as withsubstrate layer 3901 of FIG. 2), and it may comprise any one or more ofa variety of rigid or flexible materials such as: glass, polyethylene,polypropylene, polycarbonate, polyimide, PMMA, PET, PEN, Kapton, orquartz. In general, the term substrate is used to refer to material uponwhich the device is deposited during manufacturing. The photoactivelayer 1040 may be composed of electron donor or p-type material, and/oran electron acceptor or n-type material, and/or an ambipolarsemiconductor, which exhibits both p- and n-type materialcharacteristics, and/or an intrinsic semiconductor which exhibitsneither n-type or p-type characteristics. Photoactive layer 1040 may bea perovskite material as described herein, in some embodiments. Theactive layer or, as depicted in FIG. 1, the photo-active layer 1040, issandwiched between two electrically conductive electrode layers 1020 and1060. In FIG. 1, the electrode layer 1020 may be a transparent conductorsuch as a tin-doped indium oxide (ITO material) or other material asdescribed herein. In other embodiments second substrate 1070 and secondelectrode 1060 may be transparent. As previously noted, an active layerof some embodiments need not necessarily be photoactive, although in thedevice shown in FIG. 1, it is. The electrode layer 1060 may be analuminum material or other metal, or other conductive materials such ascarbon. Other materials may be used as is known in the art. The cell1010 also includes an interfacial layer (IFL) 1030, shown in the exampleof FIG. 1. The IFL may assist in charge separation. In otherembodiments, the IFL 1030 may comprise a multi-layer IFL, which isdiscussed in greater detail below. There also may be an IFL 1050adjacent to electrode 1060. In some embodiments, the IFL 1050 adjacentto electrode 1060 may also or instead comprise a multi-layer IFL (again,discussed in greater detail below). An IFL according to some embodimentsmay be semiconducting in character and may be either intrinsic,ambipolar, p-type, or n-type, or it may be dielectric in character. Insome embodiments, the IFL on the cathode side of the device (e.g., IFL1050 as shown in FIG. 1) may be p-type, and the IFL on the anode side ofthe device (e.g., IFL 1030 as shown in FIG. 1) may be n-type. In otherembodiments, however, the cathode-side IFL may be n-type and theanode-side IFL may be p-type. The cell 1010 may be attached toelectrical leads by electrodes 1060 and 1020 and a discharge unit, suchas a battery, motor, capacitor, electric grid, or any other electricalload.

Various embodiments of the present disclosure provide improved materialsand/or designs in various aspects of solar cell and other devices,including among other things, active materials (including hole-transportand/or electron-transport layers), interfacial layers, and overalldevice design.

Interfacial Layers

The present disclosure, in some embodiments, provides advantageousmaterials and designs of one or more interfacial layers within a PV,including thin-coat IFLs. Thin-coat IFLs may be employed in one or moreIFLs of a PV according to various embodiments discussed herein.

According to various embodiments, devices may optionally include aninterfacial layer between any two other layers and/or materials,although devices need not contain any interfacial layers. For example, aperovskite material device may contain zero, one, two, three, four,five, or more interfacial layers (such as the example device of FIG. 2,which contains five interfacial layers 3903, 3905, 3907, 3909, and3911). An interfacial layer may include any suitable material forenhancing charge transport and/or collection between two layers ormaterials; it may also help prevent or reduce the likelihood of chargerecombination once a charge has been transported away from one of thematerials adjacent to the interfacial layer. An interfacial layer mayadditionally physically and electrically homogenize its substrates tocreate variations in substrate roughness, dielectric constant, adhesion,creation or quenching of defects (e.g., charge traps, surface states).Suitable interfacial materials may include any one or more of: Ag; Al;Au; B; Bi; Ca; Cd; Ce; Co; Cu; Fe; Ga; Ge; H; In; Mg; Mn; Mo; Nb; Ni;Pt; Sb; Sc; Si; Sn; Ta; Ti; V; W; Y; Zn; Zr; carbides of any of theforegoing metals (e.g., SiC, Fe₃C, WC, VC, MoC, NbC); silicides of anyof the foregoing metals (e.g., Mg₂Si, SrSi₂, Sn₂Si); oxides of any ofthe foregoing metals (e.g., alumina, silica, titania, SnO₂, ZnO, NiO,ZrO₂, HfO₂), include transparent conducting oxides (“TCOs”) such asindium tin oxide, aluminum doped zinc oxide (AZO), cadmium oxide (CdO),and fluorine doped tin oxide (FTO); sulfides of any of the foregoingmetals (e.g., CdS, MoS₂, SnS₂); nitrides of any of the foregoing metals(e.g., GaN, Mg₃N₂, TiN, BN, Si₃N₄); selenides of any of the foregoingmetals (e.g., CdSe, FeSe₂, ZnSe); tellurides of any of the foregoingmetals (e.g., CdTe, TiTe₂, ZnTe); phosphides of any of the foregoingmetals (e.g., InP, GaP, GaInP); arsenides of any of the foregoing metals(e.g., CoAs₃, GaAs, InGaAs, NiAs); antimonides of any of the foregoingmetals (e.g., AlSb, GaSb, InSb); halides of any of the foregoing metals(e.g., CuCl, CuI, BiI₃); pseudohalides of any of the foregoing metals(e.g., CuSCN, AuCN, Fe(SCN)₂); carbonates of any of the foregoing metals(e.g., CaCO₃, Ce₂(CO₃)₃); functionalized or non-functionalized alkylsilyl groups; graphite; graphene; fullerenes; carbon nanotubes; anymesoporous material and/or interfacial material discussed elsewhereherein; and combinations thereof (including, in some embodiments,bilayers, trilayers, or multi-layers of combined materials). In someembodiments, an interfacial layer may include perovskite material.Further, interfacial layers may comprise doped embodiments of anyinterfacial material mentioned herein (e.g., Y-doped ZnO, N-dopedsingle-wall carbon nanotubes). Interfacial layers may also comprise acompound having three of the above materials (e.g., CuTiO₃, Zn₂SnO₄) ora compound having four of the above materials (e.g., CoNiZnO). Thematerials listed above may be present in a planar, mesoporous orotherwise nano-structured form (e.g. rods, spheres, flowers, pyramids),or aerogel structure.

First, as previously noted, one or more IFLs (e.g., either or both IFLs2626 and 2627 as shown in FIG. 1) may comprise a photoactive organiccompound of the present disclosure as a self-assembled monolayer (SAM)or as a thin film. When a photoactive organic compound of the presentdisclosure is applied as a SAM, it may comprise a binding group throughwhich it may be covalently or otherwise bound to the surface of eitheror both of the anode and cathode. The binding group of some embodimentsmay comprise any one or more of COOH, SiX₃ (where X may be any moietysuitable for forming a ternary silicon compound, such as Si(OR)₃ andSiCl₃), SO₃, PO₄H, OH, CH₂X (where X may comprise a Group 17 halide),and O. The binding group may be covalently or otherwise bound to anelectron-withdrawing moiety, an electron donor moiety, and/or a coremoiety. The binding group may attach to the electrode surface in amanner so as to form a directional, organized layer of a single molecule(or, in some embodiments, multiple molecules) in thickness (i.e., wheremultiple photoactive organic compounds are bound to the anode and/orcathode). As noted, the SAM may attach via covalent interactions, but insome embodiments, it may attach via ionic, hydrogen-bonding, and/ordispersion force (i.e., Van Der Waals) interactions. Furthermore, incertain embodiments, upon light exposure, the SAM may enter into azwitterionic excited state, thereby creating a highly-polarized IFL,which may direct charge carriers from an active layer into an electrode(e.g., either the anode or cathode). This enhanced charge-carrierinjection may, in some embodiments, be accomplished by electronicallypoling the cross-section of the active layer and therefore increasingcharge-carrier drift velocities towards their respective electrode(e.g., hole to anode; electrons to cathode). Molecules for anodeapplications of some embodiments may comprise tunable compounds thatinclude a primary electron donor moiety bound to a core moiety, which inturn is bound to an electron-withdrawing moiety, which in turn is boundto a binding group. In cathode applications according to someembodiments, IFL molecules may comprise a tunable compound comprising anelectron poor moiety bound to a core moiety, which in turn is bound toan electron donor moiety, which in turn is bound to a binding group.When a photoactive organic compound is employed as an IFL according tosuch embodiments, it may retain photoactive character, although in someembodiments it need not be photoactive.

Metal oxides may be used in thin film IFLs of some embodiments and mayinclude semiconducting metal oxides, such as NiO, SnO₂ WO₃, V₂O₅, orMoO₃. The embodiment wherein the second (e.g., n-type) active materialcomprises TiO₂ coated with a thin-coat IFL comprising Al₂O₃ could beformed, for example, with a precursor material such as Al(NO₃)₃.xH₂O, orany other material suitable for depositing Al₂O₃ onto the TiO₂, followedby thermal annealing and dye coating. In example embodiments wherein aMoO₃ coating is instead used, the coating may be formed with a precursormaterial such as Na₂MO₄.2H₂O; whereas a V₂O₅ coating according to someembodiments may be formed with a precursor material such as NaVO₃; and aWO₃ coating according to some embodiments may be formed with a precursormaterial such as NaWO₄.H₂O. The concentration of precursor material(e.g., Al(NO₃)₃.xH₂O) may affect the final film thickness (here, ofAl₂O₃) deposited on the TiO₂ or other active material. Thus, modifyingthe concentration of precursor material may be a method by which thefinal film thickness may be controlled. For example, greater filmthickness may result from greater precursor material concentration.Greater film thickness may not necessarily result in greater PCE in a PVdevice comprising a metal oxide coating. Thus, a method of someembodiments may include coating a TiO₂ (or other mesoporous) layer usinga precursor material having a concentration in the range ofapproximately 0.5 to 10.0 mM; other embodiments may include coating thelayer with a precursor material having a concentration in the range ofapproximately 2.0 to 6.0 mM; or, in other embodiments, approximately 2.5to 5.5 mM.

Furthermore, although referred to herein as Al₂O₃ and/or alumina, itshould be noted that various ratios of aluminum and oxygen may be usedin forming alumina. Thus, although some embodiments discussed herein aredescribed with reference to Al₂O₃, such description is not intended todefine a required ratio of aluminum in oxygen. Rather, embodiments mayinclude any one or more aluminum-oxide compounds, each having analuminum oxide ratio according to Al_(x)O_(y), where x may be any value,integer or non-integer, between approximately 1 and 100. In someembodiments, x may be between approximately 1 and 3 (and, again, neednot be an integer). Likewise, y may be any value, integer ornon-integer, between 0.1 and 100. In some embodiments, y may be between2 and 4 (and, again, need not be an integer). In addition, variouscrystalline forms of Al_(x)O_(y) may be present in various embodiments,such as alpha, gamma, and/or amorphous forms of alumina.

Likewise, although referred to herein as NiO, MoO₃, WO₃, and V₂O₅, suchcompounds may instead or in addition be represented as Ni_(x)O_(y)Mo_(x)O_(y), W_(x)O_(y), and V_(x)O_(y), respectively. Regarding each ofMo_(x)O_(y) and W_(x)O_(y), x may be any value, integer or non-integer,between approximately 0.5 and 100; in some embodiments, it may bebetween approximately 0.5 and 1.5. Likewise, y may be any value, integeror non-integer, between approximately 1 and 100. In some embodiments, ymay be any value between approximately 1 and 4. Regarding V_(x)O_(y), xmay be any value, integer or non-integer, between approximately 0.5 and100; in some embodiments, it may be between approximately 0.5 and 1.5.Likewise, y may be any value, integer or non-integer, betweenapproximately 1 and 100; in certain embodiments, it may be an integer ornon-integer value between approximately 1 and 10. In some embodiments, xand y may have values so as to be in a non-stoichiometric ratio. It isnoted that any IFL materials written as stoichiometric formulations inthe present disclosure may also exist in non-stoichiometric formulationssuch as examples described above.

In some embodiments, the IFL may comprise a titanate. A titanateaccording to some embodiments may be of the general formula M′TiO₃,where M′ comprises any 2+ cation. In some embodiments, M′ may comprise acationic form of Be, Mg, Ca, Sr, Ba, Ni, Zn, Cd, Hg, Cu, Pd, Pt, Sn, orPb. In some embodiments, the IFL may comprise a single species oftitanate, which in other embodiments, the IFL may comprise two or moredifferent species of titanates. In one embodiment, the titanate has theformula SrTiO₃. In another embodiment, the titanate may have the formulaBaTiO₃. In yet another embodiment, the titanate may have the formulaCaTiO₃.

By way of explanation, and without implying any limitation, titanateshave a perovskite crystalline structure and strongly seed the perovskitematerial (e.g., methylammonium lead iodide (MAPbI₃), and formamidiniumlead iodide (FAPbI₃)) growth conversion process. Titanates generallyalso meet other IFL requirements, such as ferroelectric behavior,sufficient charge carrier mobility, optical transparency, matched energylevels, and high dielectric constant.

In other embodiments, the IFL may comprise a zirconate. A zirconateaccording to some embodiments may be of the general formula M′ZrO₃,where M′ comprises any 2+ cation. In some embodiments, M′ may comprise acationic form of Be, Mg, Ca, Sr, Ba, Ni, Zn, Cd, Hg, Cu, Pd, Pt, Sn, orPb. In some embodiments, the IFL may comprise a single species ofzirconate, which in other embodiments, the IFL may comprise two or moredifferent species of zirconate. In one embodiment, the zirconate has theformula SrZrO₃. In another embodiment, the zirconate may have theformula BaZrO₃. In yet another embodiment, the zirconate may have theformula CaZrO₃.

By way of explanation, and without implying any limitation, zirconateshave a perovskite crystalline structure and strongly seed the perovskitematerial (e.g., MAPbI₃, FAPbI₃) growth conversion process. Zirconatesgenerally also meet other IFL requirements, such as ferroelectricbehavior, sufficient charge carrier mobility, optical transparency,matched energy levels, and high dielectric constant.

In other embodiments, the IFL may comprise a stannate. A stannateaccording to some embodiments may be of the general formula M′SnO₃, orM′₂SnO₄ where M′ comprises any 2+ cation. In some embodiments, M′ maycomprise a cationic form of Be, Mg, Ca, Sr, Ba, Ni, Zn, Cd, Hg, Cu, Pd,Pt, Sn, or Pb. In some embodiments, the IFL may comprise a singlespecies of stannate, which in other embodiments, the IFL may comprisetwo or more different species of stannate. In one embodiment, thestannate has the formula SrSnO₃. In another embodiment, the stannate mayhave the formula BaSnO₃. In yet another embodiment, the stannate mayhave the formula CaSnO₃.

By way of explanation, and without implying any limitation, stannateshave a perovskite crystalline structure and strongly seed the perovskitematerial (e.g., MAPbI₃, FAPbI₃) growth conversion process. Stannatesgenerally also meet other IFL requirements, such as ferroelectricbehavior, sufficient charge carrier mobility, optical transparency,matched energy levels, and high dielectric constant.

In other embodiments, the IFL may comprise a plumbate. A plumbateaccording to some embodiments may be of the general formula M′PbO₃,where M′ comprises any 2+ cation. In some embodiments, M′ may comprise acationic form of Be, Mg, Ca, Sr, Ba, Ni, Zn, Cd, Hg, Cu, Pd, Pt, Sn, orPb. In some embodiments, the IFL may comprise a single species ofplumbate, which in other embodiments, the IFL may comprise two or moredifferent species of plumbate. In one embodiment, the plumbate has theformula SrPbO₃. In another embodiment, the plumbate may have the formulaBaPbO₃. In yet another embodiment, the plumbate may have the formulaCaPbO₃. In yet another embodiment, the plumbate may have the formulaPb^(II)Pb^(IV)O₃.

By way of explanation, and without implying any limitation, plumbateshave a perovskite crystalline structure and strongly seed the perovskitematerial (e.g., MAPbI₃, FAPbI₃) growth conversion process. Plumbatesgenerally also meet other IFL requirements, such as ferroelectricbehavior, sufficient charge carrier mobility, optical transparency,matched energy levels, and high dielectric constant.

Further, in other embodiments, an IFL may comprise a combination of azirconate and a titanate in the general formula M′[Zr_(x)Ti_(1-x)]O₃,where X is greater than 0 but less than one 1, and M′ comprises any 2+cation. In some embodiments, M′ may comprise a cationic form of Be, Mg,Ca, Sr, Ba, Ni, Zn, Cd, Hg, Cu, Pd, Pt, Sn, or Pb. In some embodiments,the IFL may comprise a single species of zirconate, which in otherembodiments, the IFL may comprise two or more different species ofzirconate. In one embodiment, the zirconate/titanate combination has theformula Pb[Zr_(x)Ti_(1-x)]O₃. In another embodiment, thezirconate/titanate combination has the formula Pb[Zr_(0.52)Ti_(0.48)]O₃.

By way of explanation, and without implying any limitation, azirconate/titanate combination have a perovskite crystalline structureand strongly seed the perovskite material (e.g., MAPbI₃, FAPbI3) growthconversion process. Zirconate/titanate combinations generally also meetother IFL requirements, such as ferroelectric behavior, sufficientcharge carrier mobility, optical transparency, matched energy levels,and high dielectric constant.

In other embodiments, the IFL may comprise a niobate. A niobateaccording to some embodiments may be of the general formula M′NbO₃,where: M′ comprises any 1+ cation. In some embodiments, M′ may comprisea cationic form of Li, Na, K, Rb, Cs, Cu, Ag, Au, Tl, ammonium, or H. Insome embodiments, the IFL may comprise a single species of niobate,which in other embodiments, the IFL may comprise two or more differentspecies of niobate. In one embodiment, the niobate has the formulaLiNbO₃. In another embodiment, the niobate may have the formula NaNbO₃.In yet another embodiment, the niobate may have the formula AgNbO₃.

By way of explanation, and without implying any limitation, niobatesgenerally meet IFL requirements, such as piezoelectric behavior,non-linear optical polarizability, photoelasticity, ferroelectricbehavior, Pockels effect, sufficient charge carrier mobility, opticaltransparency, matched energy levels, and high dielectric constant.

In one embodiment, a perovskite material device may be formulated bycasting PbI₂ onto a SrTiO₃-coated ITO substrate. The PbI₂ may beconverted to MAPbI₃ by a dipping process. This process is described ingreater detail below. This resulting conversion of PbI₂ to MAPbI₃ ismore complete (as observed by optical spectroscopy) as compared to thepreparation of the substrate without SrTiO₃.

Any interfacial material discussed herein may further comprise dopedcompositions. To modify the characteristics (e.g., electrical, optical,mechanical) of an interfacial material, a stoichiometric ornon-stoichiometric material may be doped with one or more elements(e.g., Na, Y, Mg, N, P) in amounts ranging from as little as 1 ppb to 50mol %. Some examples of interfacial materials include: NiO, TiO₂,SrTiO₃, Al₂O₃, ZrO₂, WO₃, V₂O₅, MO₃, ZnO, graphene, and carbon black.Examples of possible dopants for these interfacial materials include:Li, Na, Be, Mg, Ca, Sr, Ba, Sc, Y, Nb, Ti, Fe, Co, Ni, Cu, Ga, Sn, In,B, N, P, C, S, As, a halide, a pseudohalide (e.g., cyanide, cyanate,isocyanate, fulminate, thiocyanate, isothiocyanate, azide,tetracarbonylcobaltate, carbamoyldicyanomethanide,dicyanonitrosomethanide, dicyanamide, and tricyanomethanide), and Al inany of its oxidation states. References herein to doped interfacialmaterials are not intended to limit the ratios of component elements ininterfacial material compounds.

In some embodiments, multiple IFLs made from different materials may bearranged adjacent to each other to form a composite IFL. Thisconfiguration may involve two different IFLs, three different IFLs, oran even greater number of different IFLs. The resulting multi-layer IFLor composite IFL may be used in lieu of a single-material IFL. Forexample, a composite IFL may be used any IFL shown in the example ofFIG. 2, such as IFL 3903, IFL 3905, IFL 3907, IFL 3909, or IFL 3911.While the composite IFL differs from a single-material IFL, the assemblyof a perovskite material PV cell having multi-layer IFLs is notsubstantially different than the assembly of a perovskite material PVcell having only single-material IFLs.

Generally, the composite IFL may be made using any of the materialsdiscussed herein as suitable for an IFL. In one embodiment, the IFLcomprises a layer of Al₂O₃ and a layer of ZnO or M:ZnO (doped ZnO, e.g.,Be:ZnO, Mg:ZnO, Ca:ZnO, Sr:ZnO, Ba:ZnO, Sc:ZnO, Y:ZnO, Nb:ZnO). In anembodiment, the IFL comprises a layer of ZrO₂ and a layer of ZnO orM:ZnO. In certain embodiments, the IFL comprises multiple layers. Insome embodiments, a multi-layer IFL generally has a conductor layer, adielectric layer, and a semi-conductor layer. In particular embodimentsthe layers may repeat, for example, a conductor layer, a dielectriclayer, a semi-conductor layer, a dielectric layer, and a semi-conductorlayer. Examples of multi-layer IFLs include an IFL having an ITO layer,an Al₂O₃ layer, a ZnO layer, and a second Al₂O₃ layer; an IFL having anITO layer, an Al₂O₃ layer, a ZnO layer, a second Al₂O₃ layer, and asecond ZnO layer; an IFL having an ITO layer, an Al₂O₃ layer, a ZnOlayer, a second Al₂O₃ layer, a second ZnO layer, and a third Al₂O₃layer; and IFLs having as many layers as necessary to achieve thedesired performance characteristics. As discussed previously, referencesto certain stoichiometric ratios are not intended to limit the ratios ofcomponent elements in IFL layers according to various embodiments.

Arranging two or more adjacent IFLs as a composite IFL may outperform asingle IFL in perovskite material PV cells where attributes from eachIFL material may be leveraged in a single IFL. For example, in thearchitecture having an ITO layer, an Al₂O₃ layer, and a ZnO layer, whereITO is a conducting electrode, Al₂O₃ is a dielectric material and ZnO isa n-type semiconductor, ZnO acts as an electron acceptor with wellperforming electron transport properties (e.g., mobility). Additionally,Al₂O₃ is a physically robust material that adheres well to ITO,homogenizes the surface by capping surface defects (e.g., charge traps),and improves device diode characteristics through suppression of darkcurrent.

Additionally, some perovskite material PV cells may include so called“tandem” PV cells having more than one perovskite photoactive layer. Forexample, both photoactive materials 3908 and 3906 of FIG. 2 may beperovskite materials. In such tandem PV cells an interfacial layerbetween the two photoactive layers, such as IFL 3907 (i.e., arecombination layer) of FIG. 2 may comprise a multi-layer, or composite,IFL. In some embodiments, the layers sandwiched between the twophotoactive layers of a tandem PV device may include an electrode layer.

A tandem PV device may include the following layers, listed in orderfrom either top to bottom or bottom to top: a first substrate, a firstelectrode, a first interfacial layer, a first perovskite material, asecond interfacial layer, a second electrode, a third interfacial layer,a second perovskite material, a fourth interfacial layer, and a thirdelectrode. In some embodiments, the first and third interfacial layersmay be hole transporting interfacial layers and the second and fourthinterfacial layers may be electron transporting interfacial layers. Inother embodiments, the first and third interfacial layers may beelectron transporting interfacial layers and the second and fourthinterfacial layers may be hole transporting interfacial layers. In yetother embodiments, the first and fourth interfacial layers may be holetransporting interfacial layers and the second and third interfaciallayers may be electron transporting interfacial layers. In otherembodiments, the first and fourth interfacial layers may be electrontransporting interfacial layers and the second and third interfaciallayers may be hole transporting interfacial layers. In tandem PV devicesthe first and second perovskite materials may have different band gaps.In some embodiments, the first perovskite material may be formamidiniumlead bromide (FAPbBr₃) and the second perovskite material may beformamidinium lead iodide (FAPbI₃). In other embodiments, the firstperovskite material may be methylammonium lead bromide (MAPbBr₃) and thesecond perovskite material may be formamidinium lead iodide (FAPbI₃). Inother embodiments, the first perovskite material may be methylammoniumlead bromide (MAPbBr₃) and the second perovskite material may bemethylammonium lead iodide (MAPbI₃).

Perovskite Material

A perovskite material may be incorporated into one or more aspects of aPV or other device. A perovskite material according to some embodimentsmay be of the general formula C_(w)M_(y)X_(z), where: C comprises one ormore cations (e.g., an amine, ammonium, phosphonium, a Group 1 metal, aGroup 2 metal, and/or other cations or cation-like compounds); Mcomprises one or more metals (examples including Be, Mg, Ca, Sr, Ba, Fe,Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd,Hg, and Zr); X comprises one or more anions; and w, y, and z representreal numbers between 1 and 20. In some embodiments, C may include one ormore organic cations. In some embodiments, each organic cation C may belarger than each metal M, and each anion X may be capable of bondingwith both a cation C and a metal M. In particular embodiments, aperovskite material may be of the formula CMX₃.

In certain embodiments, C may include an ammonium, an organic cation ofthe general formula [NR₄]⁺ where the R groups may be the same ordifferent groups. Suitable R groups include, but are not limited to:hydrogen, methyl, ethyl, propyl, butyl, pentyl group or isomer thereof;any alkane, alkene, or alkyne CxHy, where x=1-20, y=1-42, cyclic,branched or straight-chain; alkyl halides, CxHyXz, x=1-20, y=0-42,z=1-42, X═F, Cl, Br, or I; any aromatic group (e.g., phenyl, alkylphenl,alkoxyphenyl, pyridine, naphthalene); cyclic complexes where at leastone nitrogen is contained within the ring (e.g., pyridine, pyrrole,pyrrolidine, piperidine, tetrahydroquinoline); any sulfur-containinggroup (e.g., sulfoxide, thiol, alkyl sulfide); any nitrogen-containinggroup (nitroxide, amine); any phosphorous containing group (phosphate);any boron-containing group (e.g., boronic acid); any organic acid (e.g.,acetic acid, propanoic acid); and ester or amide derivatives thereof;any amino acid (e.g., glycine, cysteine, proline, glutamic acid,arginine, serine, histidine, 5-ammoniumvaleric acid) including alpha,beta, gamma, and greater derivatives; any silicon containing group(e.g., siloxane); and any alkoxy or group, —OCxHy, where x=0-20, y=1-42.

In certain embodiments, C may include a formamidinium, an organic cationof the general formula [R₂NCRNR₂]⁺ where the R groups may be the same ordifferent groups. Suitable R groups include, but are not limited to:hydrogen, methyl, ethyl, propyl, butyl, pentyl group or isomer thereof;any alkane, alkene, or alkyne CxHy, where x=1-20, y=1-42, cyclic,branched or straight-chain; alkyl halides, CxHyXz, x=1-20, y=0-42,z=1-42, X═F, Cl, Br, or I; any aromatic group (e.g., phenyl, alkylphenl,alkoxyphenyl, pyridine, naphthalene); cyclic complexes where at leastone nitrogen is contained within the ring (e.g., imidazole,benzimidazole, pyrimidine, (azolidinylidenemethyl)pyrrolidine,triazole); any sulfur-containing group (e.g., sulfoxide, thiol, alkylsulfide); any nitrogen-containing group (nitroxide, amine); anyphosphorous containing group (phosphate); any boron-containing group(e.g., boronic acid); any organic acid (acetic acid, propanoic acid) andester or amide derivatives thereof; any amino acid (e.g., glycine,cysteine, proline, glutamic acid, arginine, serine, histidine,5-ammoniumvaleric acid) including alpha, beta, gamma, and greaterderivatives; any silicon containing group (e.g., siloxane); and anyalkoxy or group, —OCxHy, where x=0-20, y=1-42.

Formula 1 illustrates the structure of a formamidinium cation having thegeneral formula of [R₂NCRNR₂]⁺ as described above. Formula 2 illustratesexamples structures of several formamidinium cations that may serve as acation “C” in a perovskite material.

In certain embodiments, C may include a guanidinium, an organic cationof the general formula [(R₂N)₂C═NR₂]⁺ where the R groups may be the sameor different groups. Suitable R groups include, but are not limited to:hydrogen, methyl, ethyl, propyl, butyl, pentyl group or isomer thereof;any alkane, alkene, or alkyne CxHy, where x=1-20, y=1-42, cyclic,branched or straight-chain; alkyl halides, CxHyXz, x=1-20, y=0-42,z=1-42, X═F, Cl, Br, or I; any aromatic group (e.g., phenyl,alkylphenyl, alkoxyphenyl, pyridine, naphthalene); cyclic complexeswhere at least one nitrogen is contained within the ring (e.g.,octahydropyrimido[1,2-a]pyrimidine, pyrimido[1,2-a]pyrimidine,hexahydroimidazo[1,2-a]imidazole, hexahydropyrimidin-2-imine); anysulfur-containing group (e.g., sulfoxide, thiol, alkyl sulfide); anynitrogen-containing group (nitroxide, amine); any phosphorous containinggroup (phosphate); any boron-containing group (e.g., boronic acid); anyorganic acid (acetic acid, propanoic acid) and ester or amidederivatives thereof; any amino acid (e.g., glycine, cysteine, proline,glutamic acid, arginine, serine, histidine, 5-ammoniumvaleric acid)including alpha, beta, gamma, and greater derivatives; any siliconcontaining group (e.g., siloxane); and any alkoxy or group, —OCxHy,where x=0-20, y=1-42.

Formula 3 illustrates the structure of a guanidinium cation having thegeneral formula of [(R₂N)₂C═NR₂]⁺ as described above. Formula 4illustrates examples of structures of several guanidinium cations thatmay serve as a cation “C” in a perovskite material.

In certain embodiments, C may include an ethene tetramine cation, anorganic cation of the general formula [(R₂N)₂C═C(NR₂)₂]⁺ where the Rgroups may be the same or different groups. Suitable R groups include,but are not limited to: hydrogen, methyl, ethyl, propyl, butyl, pentylgroup or isomer thereof; any alkane, alkene, or alkyne CxHy, wherex=1-20, y=1-42, cyclic, branched or straight-chain; alkyl halides,CxHyXz, x=1-20, y=0-42, z=1-42, X═F, Cl, Br, or I; any aromatic group(e.g., phenyl, alkylphenl, alkoxyphenyl, pyridine, naphthalene); cycliccomplexes where at least one nitrogen is contained within the ring(e.g., 2-hexahydropyrimidin-2-ylidenehexahydropyrimidine,octahydropyrazino[2,3-b]pyrazine, pyrazino[2,3-b]pyrazine,quinoxalino[2,3-b]quinoxaline); any sulfur-containing group (e.g.,sulfoxide, thiol, alkyl sulfide); any nitrogen-containing group(nitroxide, amine); any phosphorous containing group (phosphate); anyboron-containing group (e.g., boronic acid); any organic acid (aceticacid, propanoic acid) and ester or amide derivatives thereof; any aminoacid (e.g., glycine, cysteine, proline, glutamic acid, arginine, serine,histidine, 5-ammoniumvaleric acid) including alpha, beta, gamma, andgreater derivatives; any silicon containing group (e.g., siloxane); andany alkoxy or group, —OCxHy, where x=0-20, y=1-42.

Formula 5 illustrates the structure of an ethene tetramine cation havingthe general formula of [(R₂N)₂C═C(NR₂)₂]⁺ as described above. Formula 6illustrates examples of structures of several ethene tetramine ions thatmay serve as a cation “C” in a perovskite material.

In certain embodiments, C may include an imidazolium cation, anaromatic, cyclic organic cation of the general formula [CRNRCRNRCR]⁺where the R groups may be the same or different groups. Suitable Rgroups may include, but are not limited to: hydrogen, methyl, ethyl,propyl, butyl, pentyl group or isomer thereof, any alkane, alkene, oralkyne CxHy, where x=1-20, y=1-42, cyclic, branched or straight-chain;alkyl halides, CxHyXz, x=1-20, y=0-42, z=1-42, X═F, Cl, Br, or I; anyaromatic group (e.g., phenyl, alkylphenyl, alkoxyphenyl, pyridine,naphthalene); cyclic complexes where at least one nitrogen is containedwithin the ring (e.g.,2-hexahydropyrimidin-2-ylidenehexahydropyrimidine,octahydropyrazino[2,3-b]pyrazine, pyrazino[2,3-b]pyrazine,quinoxalino[2,3-b]quinoxaline); any sulfur-containing group (e.g.,sulfoxide, thiol, alkyl sulfide); any nitrogen-containing group(nitroxide, amine); any phosphorous containing group (phosphate); anyboron-containing group (e.g., boronic acid); any organic acid (aceticacid, propanoic acid) and ester or amide derivatives thereof; any aminoacid (e.g., glycine, cysteine, proline, glutamic acid, arginine, serine,histidine, 5-ammoniumvaleric acid) including alpha, beta, gamma, andgreater derivatives; any silicon containing group (e.g., siloxane); andany alkoxy or group, —OCxHy, where x=0-20, y=1-42.

In certain embodiments, C may include a pyridium cation, an aromatic,cyclic organic cation of the general formula [CRCRCRCRCRNR]⁺ where the Rgroups may be the same or different groups. Suitable R groups mayinclude, but are not limited to: hydrogen, methyl, ethyl, propyl, butyl,pentyl group or isomer thereof, any alkane, alkene, or alkyne CxHy,where x=1-20, y=1-42, cyclic, branched or straight-chain; alkyl halides,CxHyXz, x=1-20, y=0-42, z=1-42, X═F, Cl, Br, or I; any aromatic group(e.g., phenyl, alkylphenyl, alkoxyphenyl, pyridine, naphthalene); cycliccomplexes where at least one nitrogen is contained within the ring(e.g., 2-hexahydropyrimidin-2-ylidenehexahydropyrimidine,octahydropyrazino[2,3-b]pyrazine, pyrazino[2,3-b]pyrazine,quinoxalino[2,3-b]quinoxaline); any sulfur-containing group (e.g.,sulfoxide, thiol, alkyl sulfide); any nitrogen-containing group(nitroxide, amine); any phosphorous containing group (phosphate); anyboron-containing group (e.g., boronic acid); any organic acid (aceticacid, propanoic acid) and ester or amide derivatives thereof; any aminoacid (e.g., glycine, cysteine, proline, glutamic acid, arginine, serine,histidine, 5-ammoniumvaleric acid) including alpha, beta, gamma, andgreater derivatives; any silicon containing group (e.g., siloxane); andany alkoxy or group, —OCxHy, where x=0-20, y=1-42.

In some embodiments, X may include one or more halides. In certainembodiments, X may instead or in addition include a Group 16 anion. Incertain embodiments, the Group 16 anion may be oxide, sulfide, selenide,or telluride. In certain embodiments, X may instead or in additioninclude one or more a pseudohalides (e.g., cyanide, cyanate, isocyanate,fulminate, thiocyanate, isothiocyanate, azide, tetracarbonylcobaltate,carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide, andtricyanomethanide).

In one embodiment, a perovskite material may comprise the empiricalformula CMX₃ where: C comprises one or more of the aforementionedcations, a Group 1 metal, a Group 2 metal, and/or other cations orcation-like compounds; M comprises one or more metals (examplesincluding Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge,Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr); and X comprises one ormore of the aforementioned anions.

In another embodiment, a perovskite material may comprise the empiricalformula C′M₂X₆ where: C′ comprises a cation with a 2+ charge includingone or more of the aforementioned cations, diammonium butane, a Group 1metal, a Group 2 metal, and/or other cations or cation-like compounds; Mcomprises one or more metals (examples including Be, Mg, Ca, Sr, Ba, Fe,Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd,Hg, and Zr); and X comprises one or more of the aforementioned anions.

In another embodiment, a perovskite material may comprise the empiricalformula C′MX₄ where: C′ comprises a cation with a 2+ charge includingone or more of the aforementioned cations, diammonium butane, a Group 1metal, a Group 2 metal, and/or other cations or cation-like compounds; Mcomprises one or more metals (examples including Be, Mg, Ca, Sr, Ba, Fe,Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd,Hg, and Zr); and X comprises one or more of the aforementioned anions.In such an embodiment, the perovskite material may have a 2D structure.

In one embodiment, a perovskite material may comprise the empiricalformula C₃M₂X₉ where: C comprises one or more of the aforementionedcations, a Group 1 metal, a Group 2 metal, and/or other cations orcation-like compounds; M comprises one or more metals (examplesincluding Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge,Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr); and X comprises one ormore of the aforementioned anions.

In one embodiment, a perovskite material may comprise the empiricalformula CM₂X₇ where: C comprises one or more of the aforementionedcations, a Group 1 metal, a Group 2 metal, and/or other cations orcation-like compounds; M comprises one or more metals (examplesincluding Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge,Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr n); and X comprises oneor more of the aforementioned anions.

In one embodiment, a perovskite material may comprise the empiricalformula C₂MX₄ where: C comprises one or more of the aforementionedcations, a Group 1 metal, a Group 2 metal, and/or other cations orcation-like compounds; M comprises one or more metals (examplesincluding Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge,Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr); and X comprises one ormore of the aforementioned anions.

Perovskite materials may also comprise mixed ion formulations where C,M, or X comprise two or more species, for example,Cs_(0.1)FA_(0.9)Pb(I_(0.9)Cl_(0.1))₃;Rb_(0.1)FA_(0.9)Pb(I_(0.9)Cl_(0.1))₃Cs_(0.1)FA_(0.9)PbI₃;FAPb_(0.5)Sn_(0.5)I₃; FA_(0.93)Cs_(0.17)Pb(I_(0.6)Br_(0.4))₃;FA_(0.83)Cs_(0.12)Rb_(0.05)Pb(I_(0.6)Br_(0.4))₃ andFA_(0.85)MA_(0.15)Pb(I_(0.85)Br_(0.15))₃.

Composite Perovskite Material Device Design

In some embodiments, the present disclosure may provide composite designof PV and other similar devices (e.g., batteries, hybrid PV batteries,FETs, LEDs, nonlinear optics (NLOs), waveguides, etc.) including one ormore perovskite materials. For example, one or more perovskite materialsmay serve as either or both of first and second active material of someembodiments (e.g., active materials 3906 a and 3908 a of FIG. 3). Inmore general terms, some embodiments of the present disclosure providePV or other devices having an active layer comprising one or moreperovskite materials. In such embodiments, perovskite material (that is,material including any one or more perovskite materials(s)) may beemployed in active layers of various architectures. Furthermore,perovskite material may serve the function(s) of any one or morecomponents of an active layer (e.g., charge transport material,mesoporous material, photoactive material, and/or interfacial material,each of which is discussed in greater detail below). In someembodiments, the same perovskite materials may serve multiple suchfunctions, although in other embodiments, a plurality of perovskitematerials may be included in a device, each perovskite material servingone or more such functions. In certain embodiments, whatever role aperovskite material may serve, it may be prepared and/or present in adevice in various states. For example, it may be substantially solid insome embodiments. A solution or suspension may be coated or otherwisedeposited within a device (e.g., on another component of the device suchas a mesoporous, interfacial, charge transport, photoactive, or otherlayer, and/or on an electrode). Perovskite materials in some embodimentsmay be formed in situ on a surface of another component of a device(e.g., by vapor deposition as a thin-film solid). Any other suitablemeans of forming a layer comprising perovskite material may be employed.

In general, a perovskite material device may include a first electrode,a second electrode, and an active layer comprising a perovskitematerial, the active layer disposed at least partially between the firstand second electrodes. In some embodiments, the first electrode may beone of an anode and a cathode, and the second electrode may be the otherof an anode and cathode. An active layer according to certainembodiments may include any one or more active layer components,including any one or more of: charge transport material; liquidelectrolyte; mesoporous material; photoactive material (e.g., a dye,silicon, cadmium telluride, cadmium sulfide, cadmium selenide, copperindium gallium selenide, gallium arsenide, germanium indium phosphide,semiconducting polymers, other photoactive materials)); and interfacialmaterial. Any one or more of these active layer components may includeone or more perovskite materials. In some embodiments, some or all ofthe active layer components may be in whole or in part arranged insub-layers. For example, the active layer may comprise any one or moreof: an interfacial layer including interfacial material; a mesoporouslayer including mesoporous material; and a charge transport layerincluding charge transport material. Further, an interfacial layer maybe included between any two or more other layers of an active layeraccording to some embodiments and/or between an active layer componentand an electrode. Reference to layers herein may include either a finalarrangement (e.g., substantially discrete portions of each materialseparately definable within the device), and/or reference to a layer maymean arrangement during construction of a device, notwithstanding thepossibility of subsequent intermixing of material(s) in each layer.Layers may in some embodiments be discrete and comprise substantiallycontiguous material (e.g., layers may be as stylistically illustrated inFIG. 2).

In some embodiments, a perovskite material device may be a field effecttransistor (FET). An FET perovskite material device may include a sourceelectrode, drain electrode, gate electrode, dielectric layer, and asemiconductor layer. In some embodiments the semiconductor layer of anFET perovskite material device may be a perovskite material.

A perovskite material device according to some embodiments mayoptionally include one or more substrates. In some embodiments, eitheror both of the first and second electrode may be coated or otherwisedisposed upon a substrate, such that the electrode is disposedsubstantially between a substrate and the active layer. The materials ofcomposition of devices (e.g., substrate, electrode, active layer and/oractive layer components) may in whole or in part be either rigid orflexible in various embodiments. In some embodiments, an electrode mayact as a substrate, thereby negating the need for a separate substrate.

Furthermore, a perovskite material device according to certainembodiments may optionally include an anti-reflective layer oranti-reflective coating (ARC). In addition, a perovskite material devicemay include any one or more additives, such as any one or more of theadditives discussed above with respect to some embodiments of thepresent disclosure.

Description of some of the various materials that may be included in aperovskite material device will be made in part with reference to FIG.2. FIG. 2 is a stylized diagram of a perovskite material device 3900according to some embodiments. Although various components of the device3900 are illustrated as discrete layers comprising contiguous material,it should be understood that FIG. 2 is a stylized diagram; thus,embodiments in accordance with it may include such discrete layers,and/or substantially intermixed, non-contiguous layers, consistent withthe usage of “layers” previously discussed herein. The device 3900includes first and second substrates 3901 and 3913. A first electrode3902 is disposed upon an inner surface of the first substrate 3901, anda second electrode 3912 is disposed on an inner surface of the secondsubstrate 3913. An active layer 3950 is sandwiched between the twoelectrodes 3902 and 3912. The active layer 3950 includes a mesoporouslayer 3904; first and second photoactive materials 3906 and 3908; acharge transport layer 3910, and several interfacial layers. FIG. 2furthermore illustrates an example device 3900 according to embodimentswherein sub-layers of the active layer 3950 are separated by theinterfacial layers, and further wherein interfacial layers are disposedupon each electrode 3902 and 3912. In particular, second, third, andfourth interfacial layers 3905, 3907, and 3909 are respectively disposedbetween each of the mesoporous layer 3904, first photoactive material3906, second photoactive material 3908, and charge transport layer 3910.First and fifth interfacial layers 3903 and 3911 are respectivelydisposed between (i) the first electrode 3902 and mesoporous layer 3904;and (ii) the charge transport layer 3910 and second electrode 3912.Thus, the architecture of the example device depicted in FIG. 2 may becharacterized as: substrate-electrode-active layer-electrode-substrate.The architecture of the active layer 3950 may be characterized as:interfacial layer-mesoporous layer-interfacial layer-photoactivematerial interfacial layer-photoactive material-interfacial layer-chargetransport layer-interfacial layer. As noted previously, in someembodiments, interfacial layers need not be present; or, one or moreinterfacial layers may be included only between certain, but not all,components of an active layer and/or components of a device.

A substrate, such as either or both of first and second substrates 3901and 3913, may be flexible or rigid. If two substrates are included, atleast one should be transparent or translucent to electromagnetic (EM)radiation (such as, e.g., UV, visible, or IR radiation). If onesubstrate is included, it may be similarly transparent or translucent,although it need not be, so long as a portion of the device permits EMradiation to contact the active layer 3950. Suitable substrate materialsinclude any one or more of: glass; sapphire; magnesium oxide (MgO);mica; polymers (e.g., PEN, PET, PEG, polyolefin, polypropylene,polyethylene, polycarbonate, PMMA, polyamide, vinyl, Kapton); ceramics;carbon; composites (e.g., fiberglass, Kevlar; carbon fiber); fabrics(e.g., cotton, nylon, silk, wool); wood; drywall; tiles (e.g. ceramic,composite, or clay); metal; steel; silver; gold; aluminum; magnesium;concrete; and combinations thereof.

As previously noted, an electrode (e.g., one of electrodes 3902 and 3912of FIG. 2) may be either an anode or a cathode. In some embodiments, oneelectrode may function as a cathode, and the other may function as ananode. Either or both electrodes 3902 and 3912 may be coupled to leads,cables, wires, or other means enabling charge transport to and/or fromthe device 3900. An electrode may constitute any conductive material,and at least one electrode should be transparent or translucent to EMradiation, and/or be arranged in a manner that allows EM radiation tocontact at least a portion of the active layer 3950. Suitable electrodematerials may include any one or more of: indium tin oxide or tin-dopedindium oxide (ITO); fluorine-doped tin oxide (FTO); cadmium oxide (CdO);zinc indium tin oxide (ZITO); aluminum zinc oxide (AZO); aluminum (Al);gold (Au); silver (Ag); calcium (Ca); chromium (Cr); copper (Cu);magnesium (Mg); titanium (Ti); steel; carbon (and allotropes thereof);doped carbon (e.g., nitrogen-doped); nanoparticles in core-shellconfigurations (e.g., silicon-carbon core-shell structure); andcombinations thereof.

Mesoporous material (e.g., the material included in mesoporous layer3904 of FIG. 2) may include any pore-containing material. In someembodiments, the pores may have diameters ranging from about 1 to about100 nm; in other embodiments, pore diameter may range from about 2 toabout 50 nm. Suitable mesoporous material includes any one or more of:any interfacial material and/or mesoporous material discussed elsewhereherein; aluminum (Al); bismuth (Bi); cerium (Ce); hafnium (Hf); indium(In); molybdenum (Mo); niobium (Nb); nickel (Ni); silicon (Si); titanium(Ti); vanadium (V); zinc (Zn); zirconium (Zr); an oxide of any one ormore of the foregoing metals (e.g., alumina, ceria, titania, zinc oxide,zirconia, etc.); a sulfide of any one or more of the foregoing metals; anitride of any one or more of the foregoing metals; and combinationsthereof. In some embodiments, any material disclosed herein as an IFLmay be a mesoporous material. In other embodiments, the deviceillustrated by FIG. 2 may not include a mesoporous material layer andinclude only thin-film, or “compact,” IFLs that are not mesoporous.

Photoactive material (e.g., first or second photoactive material 3906 or3908 of FIG. 2) may comprise any photoactive compound, such as any oneor more of silicon (for example, polycrystalline silicon,single-crystalline silicon, or amorphous silicon), cadmium telluride,cadmium sulfide, cadmium selenide, copper indium gallium selenide,copper indium selenide, copper zinc tin sulfide, gallium arsenide,germanium, germanium indium phosphide, indium phosphide, one or moresemiconducting polymers (e.g., polythiophenes (e.g.,poly(3-hexylthiophene) and derivatives thereof, or P3HT);carbazole-based copolymers such as polyheptadecanylcarbazoledithienylbenzothiadiazole and derivatives thereof (e.g., PCDTBT); othercopolymers such as polycyclopentadithiophene-benzothiadiazole andderivatives thereof (e.g., PCPDTBT),polybenzodithiophenyl-thienothiophenediyl and derivatives thereof (e.g.,PTB6, PTB7, PTB7-th, PCE-10); poly(triaryl amine) compounds andderivatives thereof (e.g., PTAA); polyphenylene vinylenes andderivatives thereof (e.g., MDMO-PPV, MEH-PPV), and combinations thereof.

In certain embodiments, photoactive material may instead or in additioncomprise a dye (e.g., N719, N3, other ruthenium-based dyes). In someembodiments, a dye (of whatever composition) may be coated onto anotherlayer (e.g., a mesoporous layer and/or an interfacial layer). In someembodiments, photoactive material may include one or more perovskitematerials. Perovskite-material-containing photoactive substance may beof a solid form, or in some embodiments it may take the form of a dyethat includes a suspension or solution comprising perovskite material.Such a solution or suspension may be coated onto other device componentsin a manner similar to other dyes. In some embodiments, solidperovskite-containing material may be deposited by any suitable means(e.g., vapor deposition, solution deposition, direct placement of solidmaterial). Devices according to various embodiments may include one,two, three, or more photoactive compounds (e.g., one, two, three, ormore perovskite materials, dyes, or combinations thereof). In certainembodiments including multiple dyes or other photoactive materials, eachof the two or more dyes or other photoactive materials may be separatedby one or more interfacial layers. In some embodiments, multiple dyesand/or photoactive compounds may be at least in part intermixed.

Charge transport material (e.g., charge transport material of chargetransport layer 3910 in FIG. 2) may include solid-state charge transportmaterial (i.e., a colloquially labeled solid-state electrolyte), or itmay include a liquid electrolyte and/or ionic liquid. Any of the liquidelectrolyte, ionic liquid, and solid-state charge transport material maybe referred to as charge transport material. As used herein, “chargetransport material” refers to any material, solid, liquid, or otherwise,capable of collecting charge carriers and/or transporting chargecarriers. For instance, in PV devices according to some embodiments, acharge transport material may be capable of transporting charge carriersto an electrode. Charge carriers may include holes (the transport ofwhich could make the charge transport material just as properly labeled“hole transport material”) and electrons. Holes may be transportedtoward an anode, and electrons toward a cathode, depending uponplacement of the charge transport material in relation to either acathode or anode in a PV or other device. Suitable examples of chargetransport material according to some embodiments may include any one ormore of: perovskite material; I⁻/I₃ ⁻; Co complexes; polythiophenes(e.g., poly(3-hexylthiophene) and derivatives thereof, or P3HT);carbazole-based copolymers such as polyheptadecanylcarbazoledithienylbenzothiadiazole and derivatives thereof (e.g., PCDTBT); othercopolymers such as polycyclopentadithiophene-benzothiadiazole andderivatives thereof (e.g., PCPDTBT),polybenzodithiophenyl-thienothiophenediyl and derivatives thereof (e.g.,PTB6, PTB7, PTB7-th, PCE-10); poly(triaryl amine) compounds andderivatives thereof (e.g., PTAA); Spiro-OMeTAD; polyphenylene vinylenesand derivatives thereof (e.g., MDMO-PPV, MEH-PPV); fullerenes and/orfullerene derivatives (e.g., C60, PCBM); carbon nanotubes; graphite;graphene; carbon black; amorphous carbon; glassy carbon; carbon fiber;and combinations thereof. In certain embodiments, charge transportmaterial may include any material, solid or liquid, capable ofcollecting charge carriers (electrons or holes), and/or capable oftransporting charge carriers. Charge transport material of someembodiments therefore may be n- or p-type active, ambipolar, and/orintrinsic semi-conducting material. Charge transport material may bedisposed proximate to one of the electrodes of a device. It may in someembodiments be disposed adjacent to an electrode, although in otherembodiments an interfacial layer may be disposed between the chargetransport material and an electrode (as shown, e.g., in FIG. 2 with thefifth interfacial layer 3911). In certain embodiments, the type ofcharge transport material may be selected based upon the electrode towhich it is proximate. For example, if the charge transport materialcollects and/or transports holes, it may be proximate to an anode so asto transport holes to the anode. However, the charge transport materialmay instead be placed proximate to a cathode and be selected orconstructed so as to transport electrons to the cathode.

As previously noted, devices according to various embodiments mayoptionally include an interfacial layer between any two other layersand/or materials, although devices according to some embodiments neednot contain any interfacial layers. Thus, for example, a perovskitematerial device may contain zero, one, two, three, four, five, or moreinterfacial layers (such as the example device of FIG. 2, which containsfive interfacial layers 3903, 3905, 3907, 3909, and 3911). Aninterfacial layer may include a thin-coat interfacial layer inaccordance with embodiments previously discussed herein (e.g.,comprising alumina and/or other metal-oxide particles, and/or atitania/metal-oxide bilayer, and/or other compounds in accordance withthin-coat interfacial layers as discussed elsewhere herein). Aninterfacial layer according to some embodiments may include any suitablematerial for enhancing charge transport and/or collection between twolayers or materials; it may also help prevent or reduce the likelihoodof charge recombination once a charge has been transported away from oneof the materials adjacent to the interfacial layer. Suitable interfacialmaterials may include any one or more of: any mesoporous material and/orinterfacial material discussed elsewhere herein; Ag; Al; Au; B; Bi; Ca;Cd; Ce; Co; Cu; Fe; Ga; Ge; H; In; Mg; Mn; Mo; Nb; Ni; Pt; Sb; Sc; Si;Sn; Ta; Ti; V; W; Y; Zn; Zr; carbides of any of the foregoing metals(e.g., SiC, Fe₃C; WC); silicides of any of the foregoing metals (e.g.,Mg₂Si, SrSi₂, Sn₂Si); oxides of any of the foregoing metals (e.g.,alumina, silica, titania, SnO₂, ZnO); sulfides of any of the foregoingmetals (e.g., CdS, MoS₂, SnS₂); nitrides of any of the foregoing metals(e.g., Mg₃N₂, TiN, BN, Si₃N₄); selenides of any of the foregoing metals(e.g., CdSe, FeSe₂, ZnSe); tellurides of any of the foregoing metals(e.g., CdTe, TiTe₂, ZnTe); phosphides of any of the foregoing metals(e.g., InP, GaP); arsenides of any of the foregoing metals (e.g., CoAs₃,GaAs, InGaAs, NiAs); antimonides of any of the foregoing metals (e.g.,AlSb, GaSb, InSb); halides of any of the foregoing metals (e.g., CuCl,CuI, BiI₃); pseudohalides of any of the foregoing metals (e.g., CuSCN,AuCN₂); carbonates of any of the foregoing metals (e.g., CaCO₃,Ce₂(CO₃)₃); functionalized or non-functionalized alkyl silyl groups;graphite; graphene; fullerenes; carbon nanotubes; any mesoporousmaterial and/or interfacial material discussed elsewhere herein; andcombinations thereof (including, in some embodiments, bilayers,trilayers, or multi-layers of combined materials). In some embodiments,an interfacial layer may include perovskite material. Further,interfacial layers may comprise doped embodiments of any interfacialmaterial mentioned herein (e.g., Y-doped ZnO, N-doped single-wall carbonnanotubes). Interfacial layers may also comprise a compound having threeof the above materials (e.g., CuTiO₃, Zn₂SnO₄) or a compound having fourof the above materials (e.g., CoNiZnO).

As an example, FIG. 3 illustrates an embodiment of a perovskite materialdevice 3900 a having a similar structure to perovskite material device3900 illustrated by FIG. 2. FIG. 3 is a stylized diagram of a perovskitematerial device 3900 a according to some embodiments. Although variouscomponents of the device 3900 a are illustrated as discrete layerscomprising contiguous material, it should be understood that FIG. 3 is astylized diagram; thus, embodiments in accordance with it may includesuch discrete layers, and/or substantially intermixed, non-contiguouslayers, consistent with the usage of “layers” previously discussedherein. FIG. 3 includes an active layers 3906 a and 3908 a. One or bothof active layers 3906 a and 3908 a may, in some embodiments, include anyperovskite photoactive materials described above with respect to FIG. 2.In other embodiments, one or both of active layers 3906 a and 3908 a mayinclude any photoactive material described herein, such as, thin filmsemiconductors (e.g., CdTe, CZTS, CIGS), photoactive polymers, dyesensitized photoactive materials, fullerenes, small molecule photoactivematerials, and crystalline and polycrystalline semiconductor materials(e.g., silicon, GaAs, InP, Ge). In yet other embodiments, one or both ofactive layers 3906 a and 3908 a may include a light emitting diode(LED), field effect transistor (FET), thin film battery layer, orcombinations thereof. In embodiments, one of active layers 3906 a and3908 a may include a photoactive material and the other may include alight emitting diode (LED), field effect transistor (FET), thin filmbattery layer, or combinations thereof. For example, active layer 3908 amay comprise a perovskite material photoactive layer and active layer3906 b may comprise a field effect transistor layer. Other layersillustrated of FIG. 3, such as layers 3901 a, 3902 a, 3903 a, 3904 a,3905 a, 3907 a (i.e., a recombination layer), 3909 a, 3910 a, 3911 a,3912 a, and 3913 a, may be analogous to such corresponding layers asdescribed herein with respect to FIG. 2.

Additionally, in some embodiments, a perovskite material may have threeor more active layers. As an example, FIG. 4 illustrates an embodimentof a perovskite material device 3900 b having a similar structure toperovskite material device 3900 illustrated by FIG. 2. FIG. 3 is astylized diagram of a perovskite material device 3900 b according tosome embodiments. Although various components of the device 3900 b areillustrated as discrete layers comprising contiguous material, it shouldbe understood that FIG. 4 is a stylized diagram; thus, embodiments inaccordance with it may include such discrete layers, and/orsubstantially intermixed, non-contiguous layers, consistent with theusage of “layers” previously discussed herein. FIG. 4 includes an activelayers 3904 b, 3906 b and 3908 b. One or more of active layers 3904 b,3906 b and 3908 b may, in some embodiments, include any perovskitephotoactive materials described above with respect to FIG. 2. In otherembodiments, one or more of active layers 3904 b, 3906 b and 3908 b mayinclude any photoactive material described herein, such as, thin filmsemiconductors (e.g., CdTe, CZTS, CIGS), photoactive polymers, dyesensitized photoactive materials, fullerenes, small molecule photoactivematerials, and crystalline and polycrystalline semiconductor materials(e.g., silicon, GaAs, InP, Ge). In yet other embodiments, one or more ofactive layers 3904 b, 3906 b and 3908 b may include a light emittingdiode (LED), field effect transistor (FET), thin film battery layer, orcombinations thereof. In embodiments, one or more of active layers ofactive layers 3904 b, 3906 b and 3908 b may include a photoactivematerial and the other may include a light emitting diode (LED), fieldeffect transistor (FET), thin film battery layer, or combinationsthereof. For example, active layer 3908 a and 3906 b may both compriseperovskite material photoactive layers and active layer 3904 b maycomprise a field effect transistor layer. Other layers illustrated ofFIG. 3, such as layers 3901 b, 3902 b, 3903 b, 3904 b, 3905 b (i.e., arecombination layer), 3907 b (i.e., a recombination layer), 3909 b, 3910b, 3911 b, 3912 b, and 3913 b, may be analogous to such correspondinglayers as described herein with respect to FIG. 2.

Additional, more specific, example embodiments of perovskite deviceswill be discussed in terms of further stylized depictions of exampledevices. The stylized nature of these depictions, FIGS. 1-4, similarlyis not intended to restrict the type of device which may in someembodiments be constructed in accordance with any one or more of FIGS.1-4. That is, the architectures exhibited in FIGS. 1-4 may be adapted soas to provide the BHJs, batteries, FETs, hybrid PV batteries, serialmulti-cell PVs, parallel multi-cell PVs and other similar devices ofother embodiments of the present disclosure, in accordance with anysuitable means (including both those expressly discussed elsewhereherein, and other suitable means, which will be apparent to thoseskilled in the art with the benefit of this disclosure).

Formulation of the Perovskite Material Active Layer

As discussed earlier, in some embodiments, a perovskite material in theactive layer may have the formulation CMX_(3-y)X′_(y) (0≥y≥3), where: Ccomprises one or more cations (e.g., an amine, ammonium, a Group 1metal, a Group 2 metal, formamidinium, guanidinium, ethene tetramine,phosphonium, imidazolium, and/or other cations or cation-likecompounds); M comprises one or more metals (e.g., Be, Mg, Ca, Sr, Ba,Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn,Cd, Hg, and Zr); and X and X′ comprise one or more anions. In oneembodiment, the perovskite material may comprise CPbI_(3-y)Cl_(y). Incertain embodiments, the perovskite material may be deposited as anactive layer in a PV device by, for example, drop casting, spin casting,slot-die printing, screen printing, or ink-jet printing onto a substratelayer using the steps described below.

First, a lead halide precursor ink is formed. An amount of lead halidemay be massed in a clean, dry vessel in a controlled atmosphereenvironment (e.g., a controlled atmosphere box with glove-containingportholes allows for materials manipulation in an air-free environment).Suitable lead halides include, but are not limited to, lead (II) iodide,lead (II) bromide, lead (II) chloride, and lead (II) fluoride. The leadhalide may comprise a single species of lead halide or it may comprise alead halide mixture in a precise ratio. In certain embodiments, the leadhalide mixture may comprise any binary, ternary, or quaternary ratio of0.001-100 mol % of iodide, bromide, chloride, or fluoride. In oneembodiment, the lead halide mixture may comprise lead (II) chloride andlead (II) iodide in a ratio of about 10:90 mol:mol. In otherembodiments, the lead halide mixture may comprise lead (II) chloride andlead (II) iodide in a ratio of about 5:95, about 7.5:92.5, or about15:85 mol:mol.

Alternatively, other lead salt precursors may be used in conjunctionwith or in lieu of lead halide salts to form the precursor ink. Suitableprecursor salts may comprise any combination of lead (II) or lead(IV)and the following anions: nitrate, nitrite, carboxylate, acetate,acetonyl acetonate, formate, oxalate, sulfate, sulfite, thiosulfate,phosphate, tetrafluoroborate, hexafluorophosphate,tetra(perfluorophenyl) borate, hydride, oxide, peroxide, hydroxide,nitride, arsenate, arsenite, perchlorate, carbonate, bicarbonate,chromate, dichromate, iodate, bromate, chlorate, chlorite, hypochlorite,hypobromite, cyanide, cyanate, isocyanate, fulminate, thiocyanate,isothiocyanate, azide, tetracarbonylcobaltate,carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide,tricyanomethanide, amide, and permanganate.

The precursor ink may further comprise a lead (II) or lead (IV) salt inmole ratios of 0 to 100% to the following metal ions Be, Mg, Ca, Sr, Ba,Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn,Cd, Hg, and Zr as a salt of the aforementioned anions.

A solvent may then be added to the vessel to dissolve the lead solids toform the lead halide precursor ink. Suitable solvents include, but arenot limited to, dry N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone,dimethylformamide, dialkylformamide, dimethylsulfoxide (DMSO), methanol,ethanol, propanol, butanol, tetrahydrofuran, formamide,tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene,dichlorobenzene, dichloromethane, chloroform, and combinations thereof.In one embodiment, the lead solids are dissolved in drydimethylformamide (DMF). The lead solids may be dissolved at atemperature between about 20° C. to about 150° C. In one embodiment, thelead solids are dissolved at about 85° C. The lead solids may bedissolved for as long as necessary to form a solution, which may takeplace over a time period up to about 72 hours. The resulting solutionforms the base of the lead halide precursor ink. In some embodiments,the lead halide precursor ink may have a lead halide concentrationbetween about 0.001M and about 10M. In one embodiment, the lead halideprecursor ink has a lead halide concentration of about 1 M.

Optionally, certain additives may be added to the lead halide precursorink to affect the final perovskite crystallinity and stability. In someembodiments, the lead halide precursor ink may further comprise an aminoacid (e.g., 5-aminovaleric acid, histidine, glycine, lysine), an aminoacid hydrohalide (e.g., 5-amino valeric acid hydrochloride), an IFLsurface-modifying (SAM) agent (such as those discussed earlier in thespecification), or a combination thereof. Amino acids suitable for leadhalide precursor inks may include, but are not limited to α-amino acids,β-amino acids, γ-amino acids, δ-amino acids, and any combinationthereof. In one embodiment, formamidinium chloride may be added to thelead halide precursor ink. In other embodiments, the halide of anycation discussed earlier in the specification may be used. In someembodiments, combinations of additives may be added to the lead halideprecursor ink including, for example, the combination of formamidiniumchloride and 5-amino valeric acid hydrochloride.

By way of explanation, and without limiting the disclosure to anyparticular theory of mechanism, it has been found that formamidiniumchloride and 5-amino valeric acid improve perovskite PV device stabilitywhen they are used as additives or counter-cations in a one-stepperovskite device fabrication. It has also been found that chloride, inthe form of PbCl₂, improves perovskite PV device performance when addedto a PbI₂ precursor solution in a two-step method. It has been foundthat the two-step perovskite thin film deposition process may beimproved by adding formamidinium chloride and/or 5-amino valeric acidhydrochloride directly to a lead halide precursor solution (e.g., PbI₂)to leverage both advantages with a single material. Other perovskitefilm deposition processes may likewise be improved by the addition offormamidinium chloride, 5-amino valeric acid hydrochloride, or PbCl₂ toa lead halide precursor solution.

The additives, including formamidinium chloride and/or 5-amino valericacid hydrochloride. may be added to the lead halide precursor ink atvarious concentrations depending on the desired characteristics of theresulting perovskite material. In one embodiment, the additives may beadded in a concentration of about 1 nM to about 1 M. In anotherembodiment, the additives may be added in a concentration of about 1 μMto about 1 M. In another embodiment, the additives may be added in aconcentration of about 1 μM to about 1 mM.

Optionally, in certain embodiments, water may be added to the leadhalide precursor ink. By way of explanation, and without limiting thedisclosure to any particular theory or mechanism, the presence of wateraffects perovskite thin-film crystalline growth. Under normalcircumstances, water may be absorbed as vapor from the air. However, itis possible to control the perovskite PV crystallinity through thedirect addition of water to the lead halide precursor ink in specificconcentrations. Suitable water includes distilled, deionized water, orany other source of water that is substantially free of contaminants(including minerals). It has been found, based on light I-V sweeps, thatthe perovskite PV light-to-power conversion efficiency may nearly triplewith the addition of water compared to a completely dry device.

The water may be added to the lead halide precursor ink at variousconcentrations depending on the desired characteristics of the resultingperovskite material. In one embodiment, the water may be added in aconcentration of about 1 nL/mL to about 1 mL/mL. In another embodiment,the water may be added in a concentration of about 1 μL/mL to about 0.1mL/mL. In another embodiment, the water may be added in a concentrationof about 1 μL/mL to about 20 μL/mL.

The lead halide precursor ink may then be deposited on the desiredsubstrate. Suitable substrate layers may include any of the substratelayers identified earlier in this disclosure. As noted above, the leadhalide precursor ink may be deposited through a variety of means,including but not limited to, drop casting, spin casting, slot-dieprinting, screen printing, or ink-jet printing. In certain embodiments,the lead halide precursor ink may be spin-coated onto the substrate at aspeed of about 500 rpm to about 10,000 rpm for a time period of about 5seconds to about 600 seconds. In one embodiment, the lead halideprecursor ink may be spin-coated onto the substrate at about 3000 rpmfor about 30 seconds. The lead halide precursor ink may be deposited onthe substrate at an ambient atmosphere in a humidity range of about 0%relative humidity to about 50% relative humidity. The lead halideprecursor ink may then be allowed to dry in a substantially water-freeatmosphere, i.e., less than 30% relative humidity, to form a thin film.

The thin film may then be thermally annealed for a time period up toabout 24 hours at a temperature of about 20° C. to about 300° C. In oneembodiment, the thin film may be thermally annealed for about tenminutes at a temperature of about 50° C. The perovskite material activelayer may then be completed by a conversion process in which theprecursor film is submerged or rinsed with a solution comprising asolvent or mixture of solvents (e.g., DMF, isopropanol, methanol,ethanol, butanol, chloroform chlorobenzene, dimethylsulfoxide, water)and salt (e.g., methylammonium iodide, formamidinium iodide, guanidiniumiodide, 1,2,2-triaminovinylammonium iodide, 5-aminovaleric acidhydroiodide) in a concentration between 0.001M and 10M. In certainembodiments, the thin films may also be thermally post-annealed in thesame fashion as in the first line of this paragraph.

In some embodiments, a lead salt precursor may be deposited onto asubstrate to form a lead salt thin film. The substrate may have atemperature about equal to ambient temperature or have a controlledtemperature between 0° C. and 500° C. The lead salt precursor may bedeposited by a variety of methods known in the art, including but notlimited to spin-coating, slot-die printing, ink-jet printing, gravureprinting, screen printing, sputtering, PE-CVD, thermal evaporation,spray coating. In certain embodiments, the deposition of the lead saltprecursor may comprise sheet-to-sheet or roll-to-roll manufacturingmethodologies. Deposition of the lead salt precursor may be performed ina variety of atmospheres at ambient pressure (e.g. about one atmosphere,depending on elevation and atmospheric conditions) or at pressures lessthan atmospheric or ambient (e.g., 1 mTorr to 500 mTorr). The depositionatmosphere may comprise ambient air, a controlled humidity environment(e.g., 0-100 g H₂O/m³ of gas), pure argon, pure nitrogen, pure oxygen,pure hydrogen, pure helium, pure neon, pure krypton, pure CO₂ or anycombination of the preceding gases. A controlled humidity environmentmay include an environment in which the absolute humidity or the %relative humidity is held at a fixed value, or in which the absolutehumidity or the % relative humidity varies according to predeterminedset points or a predetermined function. In particular embodiments,deposition may occur in a controlled humidity environment having a %relative humidity greater than or equal to 0% and less than or equal to50%. In other embodiments, deposition may occur in a controlled humidityenvironment containing greater than or equal to 0 g H₂O/m³ gas and lessthan or equal to 20 g H₂O/m³ gas.

The lead salt precursor may be a liquid, a gas, solid, or combination ofthese states of matter such as a solution, suspension, colloid, foam,gel, or aerosol. In some embodiments, the lead salt precursor may be asolution containing one or more solvents. For example, the lead saltprecursor may contain one or more of N-cyclohexyl-2-pyrrolidone,alkyl-2-pyrrolidone, dimethylformamide, dialkylformamide,dimethylsulfoxide (DMSO), acetonitrile, methanol, ethanol, propanol,butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine,alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene,dichloromethane, chloroform, and combinations thereof. The lead saltprecursor may comprise a single lead salt (e.g., lead (II) iodide, lead(II) thiocyanate) or any combination of those disclosed herein (e.g.,PbI₂+PbCl₂; PbI₂+Pb(SCN)₂). The lead salt precursor may also contain oneor more additives such as an amino acid (e.g., 5-aminovaleric acidhydroiodide), 1,8-diiodooctane, 1,8-dithiooctane, formamidinium halide,acetic acid, trifluoroacetic acid, a methylammonium halide, or water.The lead halide precursor ink may be allowed to dry in a substantiallywater-free atmosphere, i.e., less than 30% relative humidity, to form athin film. The thin film may then be thermally annealed for a timeperiod of up to about 24 hours at a temperature of about 20° C. to about300° C. Annealing may be performed in a variety of atmospheres atambient pressure (e.g. about one atmosphere, depending on elevation andatmospheric conditions) or at pressures less than atmospheric or ambient(e.g., 1 mTorr to 500 mTorr). An annealing atmosphere may compriseambient air, a controlled humidity environment (e.g., 0-100 g H₂O/m³ ofgas), pure argon, pure nitrogen, pure oxygen, pure hydrogen, purehelium, pure neon, pure krypton, pure CO₂ or any combination of thepreceding gases. A controlled humidity environment may include anenvironment in which the absolute humidity or the % relative humidity isheld at a fixed value, or in which the absolute humidity or the %relative humidity varies according to predetermined set points or apredetermined function. In particular embodiments, annealing may occurin a controlled humidity environment having a % relative humiditygreater than or equal to 0% and less than or equal to 50%. In otherembodiments, annealing may occur in a controlled humidity environmentcontaining greater than or equal to 0 g H₂O/m³ gas and less than orequal to 20 g H₂O/m³ gas

After the lead salt precursor is deposited, a second salt precursor(e.g., formamidinium iodide, formamidinium thiocyanate, guanidiniumthiocyanate) may be deposited onto the lead salt thin film, where thelead salt thin film may have a temperature about equal to ambienttemperature or have a controlled temperature between 0° C. and 500° C.The second salt precursor, in some embodiments, may be deposited atambient temperature or at elevated temperature between about 25° C. and125° C. The second salt precursor may be deposited by a variety ofmethods known in the art, including but not limited to spin-coating,slot-die printing, ink-jet printing, gravure printing, screen printing,sputtering, PE-CVD, thermal evaporation, or spray coating. Deposition ofthe second salt precursor may be performed in a variety of atmospheresat ambient pressure (e.g. about one atmosphere, depending on elevationand atmospheric conditions) or at pressures less than atmospheric orambient (e.g., 1 mTorr to 500 mTorr). The deposition atmosphere maycomprise ambient air, a controlled humidity environment (e.g., 0-100 gH₂O/m³ of gas), pure argon, pure nitrogen, pure oxygen, pure hydrogen,pure helium, pure neon, pure krypton, pure CO₂ or any combination of thepreceding gases. A controlled humidity environment may include anenvironment in which the absolute humidity or the % relative humidity isheld at a fixed value, or in which the absolute humidity or the %relative humidity varies according to predetermined set points or apredetermined function. In particular embodiments, deposition may occurin a controlled humidity environment having a % relative humiditygreater than or equal to 0% and less than or equal to 50%. In otherembodiments, deposition may occur in a controlled humidity environmentcontaining greater than or equal to 0 g H₂O/m³ gas and less than orequal to 20 g H₂O/m³ gas.

In some embodiments the second salt precursor may be a solutioncontaining one or more solvents. For example, the second salt precursormay contain one or more of dry N-cyclohexyl-2-pyrrolidone,alkyl-2-pyrrolidone, dimethylformamide, dialkylformamide,dimethylsulfoxide (DMSO), acetonitrile, methanol, ethanol, propanol,butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine,alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene,dichloromethane, chloroform, and combinations thereof.

After deposition of the lead salt precursor and second salt precursor,the substrate may be annealed. Annealing the substrate may convert thelead salt precursor and second salt precursor to a perovskite material,(e.g. FAPbI₃, GAPb(SCN)₃, FASnI₃). Annealing may be performed in avariety of atmospheres at ambient pressure (e.g. about one atmosphere,depending on elevation and atmospheric conditions) or at pressures lessthan atmospheric or ambient (e.g., 1 mTorr to 500 mTorr). An annealingatmosphere may comprise ambient air, a controlled humidity environment(e.g., 0-100 g H₂O/m³ of gas), pure argon, pure nitrogen, pure oxygen,pure hydrogen, pure helium, pure neon, pure krypton, pure CO₂ or anycombination of the preceding gases. A controlled humidity environmentmay include an environment in which the absolute humidity or the %relative humidity is held at a fixed value, or in which the absolutehumidity or the % relative humidity varies according to predeterminedset points or a predetermined function. In particular embodiments,annealing may occur in a controlled humidity environment having a %relative humidity greater than or equal to 0% and less than or equal to50%. In other embodiments, annealing may occur in a controlled humidityenvironment containing greater than or equal to 0 g H₂O/m³ gas and lessthan or equal to 20 g H₂O/m³ gas. In some embodiments, annealing mayoccur at a temperature greater than or equal to 50° C. and less than orequal to 300° C. Unless described as otherwise, any annealing ordeposition step described herein may be carried out under the precedingconditions.

For example, in a particular embodiment, a FAPbI₃ perovskite materialmay be formed by the following process. First a lead (II) halideprecursor comprising about a 90:10 mole ratio of PbI₂ to PbCl₂ dissolvedin anhydrous DMF may be deposited onto a substrate by spin-coating orslot-die printing. The lead halide precursor ink may be allowed to dryin a substantially water-free atmosphere, i.e., less than 30% relativehumidity, for approximately one hour (±15 minutes) to form a thin film.The thin film may be subsequently thermally annealed for about tenminutes at a temperature of about 50° C. (±10° C.). In otherembodiments, the lead halide precursor may be deposited by ink-jetprinting, gravure printing, screen printing, sputtering, PE-CVD,atomic-layer deposition, thermal evaporation, or spray coating. Next, aformamidinium iodide precursor comprising a 25-60 mg/mL concentration offormamidinium iodide dissolved in anhydrous isopropyl alcohol may bedeposited onto the lead halide thin film by spin coating or slot-dieprinting. In other embodiments, the formamidinium iodide precursor maybe deposited by ink-jet printing, gravure printing, screen printing,sputtering, PE-CVD, atomic-layer deposition, thermal evaporation, orspray coating. After depositing the lead halide precursor andformamidinium iodide precursor, the substrate may be annealed at about25% relative humidity (about 4 to 7 g H₂O/m³ air) and between about 125°C. and 200° C. to form a formamidinium lead iodide (FAPbI₃) perovskitematerial.

In another embodiment, a perovskite material may comprise C′CPbX₃, whereC′ is one or more Group 1 metals (i.e. Li, Na, K, Rb, Cs). In aparticular embodiment M′ may be cesium (Cs). In another embodiment C′may be rubidium (Rb). In another embodiment C′ may be sodium (Na). Inanother embodiment C′ may be potassium (K). In yet other embodiments, aperovskite material may comprise C′_(v)C_(w)Pb_(y)X_(z), where C′ is oneor more Group 1 metals and v, w, y, and z represent real numbers between1 and 20. In certain embodiments, the perovskite material may bedeposited as an active layer in a PV device by, for example, dropcasting, spin casting, gravure coating, blade coating, reverse gravurecoating, slot-die printing, screen printing, or ink-jet printing onto asubstrate layer using the steps described below.

First, a lead halide solution is formed. An amount of lead halide may bemassed in a clean, dry vessel in a controlled atmosphere environment.Suitable lead halides include, but are not limited to, lead (II) iodide,lead (II) bromide, lead (II) chloride, and lead (II) fluoride. The leadhalide may comprise a single species of lead halide or it may comprise alead halide mixture in a precise ratio. In one embodiment the leadhalide may comprise lead (II) iodide. In certain embodiments, the leadhalide mixture may comprise any binary, ternary, or quaternary ratio of0.001-100 mol % of iodide, bromide, chloride, or fluoride. In oneembodiment, the lead halide mixture may comprise lead (II) chloride andlead (II) iodide in a ratio of about 10:90 mol:mol. In otherembodiments, the lead halide mixture may comprise lead (II) chloride andlead (II) iodide in a ratio of about 5:95, about 7.5:92.5, or about15:85 mol:mol.

Alternatively, other lead salt precursors may be used in conjunctionwith or in lieu of lead halide salts to form a lead salt solution.Suitable precursor lead salts may comprise any combination of lead (II)or lead(IV) and the following anions: nitrate, nitrite, carboxylate,acetate, formate, oxalate, sulfate, sulfite, thiosulfate, phosphate,tetrafluoroborate, hexafluorophosphate, tetra(perfluorophenyl) borate,hydride, oxide, peroxide, hydroxide, nitride, arsenate, arsenite,perchlorate, carbonate, bicarbonate, chromate, dichromate, iodate,bromate, chlorate, chlorite, hypochlorite, hypobromite, cyanide,cyanate, isocyanate, fulminate, thiocyanate, isothiocyanate, azide,tetracarbonylcobaltate, carbamoyldicyanomethanide,dicyanonitrosomethanide, dicyanamide, tricyanomethanide, amide, andpermanganate.

The lead salt solution may further comprise a lead (II) or lead (IV)salt in mole ratios of 0 to 100% to the following metal ions Be, Mg, Ca,Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi,Ti, Zn, Cd, Hg, and Zr as a salt of the aforementioned anions.

A solvent may then be added to the vessel to dissolve the lead halidesolids to form the lead halide solution. Suitable solvents include, butare not limited to, dry N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone,dimethylformamide (DMF), dialkylformamide, dimethylsulfoxide (DMSO),acetonitrile, methanol, ethanol, propanol, butanol, tetrahydrofuran,formamide, tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine,chlorobenzene, dichlorobenzene, dichloromethane, chloroform, andcombinations thereof. In one embodiment, the lead solids are dissolvedin dry dimethylformamide (DMF). The lead halide solids may be dissolvedat a temperature between about 20° C. to about 150° C. In oneembodiment, the lead halide solids are dissolved at about 85° C. Thelead halide solids may be dissolved for as long as necessary to form asolution, which may take place over a time period up to about 72 hours.The resulting solution forms the base of the lead halide precursor ink.In some embodiments, the lead halide precursor ink may have a leadhalide concentration between about 0.001M and about 10M. In oneembodiment, the lead halide precursor ink has a lead halideconcentration of about 1 M. In some embodiments, the lead halidesolution may further comprise an amino acid (e.g., 5-aminovaleric acid,histidine, glycine, lysine), an amino acid hydrohalide (e.g., 5-aminovaleric acid hydrochloride), an IFL surface-modifying (SAM) agent (suchas those discussed earlier in the specification), or a combinationthereof.

Next, a Group 1 metal halide solution is formed. An amount of Group 1metal halide may be massed in a clean, dry vessel in a controlledatmosphere environment. Suitable Group 1 metal halides include, but arenot limited to, cesium iodide, cesium bromide, cesium chloride, cesiumfluoride, rubidium iodide, rubidium bromide, rubidium chloride, rubidiumfluoride, lithium iodide, lithium bromide, lithium chloride, lithiumfluoride, sodium iodide, sodium bromide, sodium chloride, sodiumfluoride, potassium iodide, potassium bromide, potassium chloride,potassium fluoride. The Group 1 metal halide may comprise a singlespecies of Group 1 metal halide or it may comprise a Group 1 metalhalide mixture in a precise ratio. In one embodiment the Group 1 metalhalide may comprise cesium iodide. In another embodiment the Group 1metal halide may comprise rubidium iodide. In another embodiment theGroup 1 metal halide may comprise sodium iodide. In another embodimentthe Group 1 metal halide may comprise potassium iodide.

Alternatively, other Group 1 metal salt precursors may be used inconjunction with or in lieu of Group 1 metal halide salts to form aGroup 1 metal salt solution. Suitable precursor Group 1 metal salts maycomprise any combination of Group 1 metals and the following anions:nitrate, nitrite, carboxylate, acetate, formate, oxalate, sulfate,sulfite, thiosulfate, phosphate, tetrafluoroborate, hexafluorophosphate,tetra(perfluorophenyl) borate, hydride, oxide, peroxide, hydroxide,nitride, arsenate, arsenite, perchlorate, carbonate, bicarbonate,chromate, dichromate, iodate, bromate, chlorate, chlorite, hypochlorite,hypobromite, cyanide, cyanate, isocyanate, fulminate, thiocyanate,isothiocyanate, azide, tetracarbonylcobaltate,carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide,tricyanomethanide, amide, and permanganate.

A solvent may then be added to the vessel to dissolve the Group 1 metalhalide solids to form the Group 1 metal halide solution. Suitablesolvents include, but are not limited to, dryN-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide(DMF), dialkylformamide, dimethylsulfoxide (DMSO), acetonitrile,methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide,tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene,dichlorobenzene, dichloromethane, chloroform, and combinations thereof.In one embodiment, the lead solids are dissolved in drydimethylsulfoxide (DMSO). The Group 1 metal halide solids may bedissolved at a temperature between about 20° C. to about 150° C. In oneembodiment, the Group 1 metal halide solids are dissolved at roomtemperature (i.e., about 25° C.). The Group 1 metal halide solids may bedissolved for as long as necessary to form a solution, which may takeplace over a time period up to about 72 hours. The resulting solutionforms the Group 1 metal halide solution. In some embodiments, the Group1 metal halide solution may have a Group 1 metal halide concentrationbetween about 0.001M and about 10M. In one embodiment, the Group 1 metalhalide solution has a Group 1 metal halide concentration of about 1 M.In some embodiments, the Group 1 metal halide solution may furthercomprise an amino acid (e.g., 5-aminovaleric acid, histidine, glycine,lysine), an amino acid hydrohalide (e.g., 5-amino valeric acidhydrochloride), an IFL surface-modifying (SAM) agent (such as thosediscussed earlier in the specification), or a combination thereof.

Next, the lead halide solution and the Group 1 metal halide solution aremixed to form a thin-film precursor ink. The lead halide solution andGroup 1 metal halide solution may be mixed in a ratio such that theresulting thin-film precursor ink has a molar concentration of the Group1 metal halide that is between 0% and 25% of the molar concentration ofthe lead halide. In particular embodiments, the thin-film precursor inkmay have a molar concentration of the Group 1 metal halide that is 1% ofthe molar concentration of the lead halide. In particular embodiments,the thin-film precursor ink may have a molar concentration of the Group1 metal halide that is 5% of the molar concentration of the lead halide.In particular embodiments, the thin-film precursor ink may have a molarconcentration of the Group 1 metal halide that is 10% of the molarconcentration of the lead halide. In particular embodiments, thethin-film precursor ink may have a molar concentration of the Group 1metal halide that is 15% of the molar concentration of the lead halide.In particular embodiments, the thin-film precursor ink may have a molarconcentration of the Group 1 metal halide that is 20% of the molarconcentration of the lead halide. In particular embodiments, thethin-film precursor ink may have a molar concentration of the Group 1metal halide that is 25% of the molar concentration of the lead halide.In some embodiments the lead halide solution and the Group 1 metalhalide solution may be stirred or agitated during or after mixing.

The thin-film precursor ink may then be deposited on the desiredsubstrate. Suitable substrate layers may include any of the substratelayers identified earlier in this disclosure. As noted above, thethin-film precursor ink may be deposited through a variety of means,including but not limited to, drop casting, spin casting, gravurecoating, blade coating, reverse gravure coating, slot-die printing,screen printing, or ink-jet printing. In certain embodiments, thethin-film precursor ink may be spin-coated onto the substrate at a speedof about 500 rpm to about 10,000 rpm for a time period of about 5seconds to about 600 seconds. In one embodiment, the thin-film precursorink may be spin-coated onto the substrate at about 3000 rpm for about 30seconds. The thin-film precursor ink may be deposited on the substrateat an ambient atmosphere in a humidity range of about 0% relativehumidity to about 50% relative humidity. The thin-film precursor ink maythen be allowed to dry in a substantially water-free atmosphere, i.e.,less than 30% relative humidity or 7 g H₂O/m³, to form a thin film.

The thin film can then be thermally annealed for a time period up toabout 24 hours at a temperature of about 20° C. to about 300° C. In oneembodiment, the thin film may be thermally annealed for about tenminutes at a temperature of about 50° C. The perovskite material activelayer may then be completed by a conversion process in which theprecursor film is submerged or rinsed with a salt solution comprising asolvent or mixture of solvents (e.g., DMF, isopropanol, methanol,ethanol, butanol, chloroform chlorobenzene, dimethylsulfoxide, water)and salt (e.g., methylammonium iodide, formamidinium iodide, guanidiniumiodide, 1,2,2-triaminovinylammonium iodide, 5-aminovaleric acidhydroiodide) in a concentration between 0.001M and 10M. In certainembodiments, the perovskite material thin films can also be thermallypost-annealed in the same fashion as in the first line of thisparagraph.

In some embodiments, the salt solution may be prepared by massing thesalt in a clean, dry vessel in a controlled atmosphere environment.Suitable salts include, but are not limited to, methylammonium iodide,formamidinium iodide, guanidinium iodide, imidazolium iodide, ethenetetramine iodide, 1,2,2-triaminovinylammonium iodide, and 5-aminovalericacid hydroiodide. Other suitable salts may include any organic cationdescribed above in the section entitled “Perovskite Material.” The saltmay comprise a single species of salt or it may comprise a salt mixturein a precise ratio. In one embodiment the salt may comprisemethylammonium iodide. In another embodiment the salt may compriseformamidinium iodide. Next, a solvent may then be added to the vessel todissolve the salt solids to form the salt solution. Suitable solventsinclude, but are not limited to, DMF, acetonitrile, isopropanol,methanol, ethanol, butanol, chloroform chlorobenzene, dimethylsulfoxide,water, and combinations thereof. In one embodiment, formamidinium iodidesalt solids are dissolved in isopropanol. The salt solids may bedissolved at a temperature between about 20° C. to about 150° C. In oneembodiment, the salt solids are dissolved at room temperature (i.e.about 25° C.). The salt solids may be dissolved for as long as necessaryto form a solution, which may take place over a time period up to about72 hours. The resulting solution forms the salt solution. In someembodiments, the salt solution may have a salt concentration betweenabout 0.001M and about 10M. In one embodiment, the salt solution has asalt concentration of about 1 M.

For example, using the process described above with a lead (II) iodidesolution, a cesium iodide solution, and a methylammonium (MA) iodidesalt solution may result in a perovskite material having the a formulaof Cs_(i)MA_(1-i)PbI₃, where i equals a number between 0 and 1. Asanother example, using a lead (II) iodide solution, a rubidium iodidesolution, and a formamidinium (FA) iodide salt solution may result in aperovskite material having the a formula of Rb_(i)FA_(1-i)PbI₃, where iequals a number between 0 and 1. As another example, using a lead (II)iodide solution, a cesium iodide solution, and a formamidinium (FA)iodide salt solution may result in a perovskite material having the aformula of Cs_(i)FA_(1-i)PbI₃, where i equals a number between 0 and 1.As another example, using a lead (II) iodide solution, a potassiumiodide solution, and a formamidinium (FA) iodide salt solution mayresult in a perovskite material having the a formula ofK_(i)FA_(1-i)PbI₃, where i equals a number between 0 and 1. As anotherexample, the using a lead (II) iodide solution, a sodium iodidesolution, and a formamidinium (FA) iodide salt solution may result in aperovskite material having the a formula of Na_(i)FA_(1-i)PbI₃, where iequals a number between 0 and 1. As another example, the using a lead(II) iodide-lead (II) chloride mixture solution, a cesium iodidesolution, and a formamidinium (FA) iodide salt solution may result in aperovskite material having the a formula ofCs_(i)FA_(1-i)PbI_(3-y)Cl_(y), where i equals a number between 0 and 1and y represents a number between 0 and 3.

In a particular embodiment, the lead halide solution as described abovemay have a ratio of 90:10 of PbI₂ to PbCl₂ on a mole basis. A cesiumiodide (CsI) solution may be added to the lead halide solution by themethod described above to form a thin film precursor ink with 10 mol %CsI. A FAPbI₃ perovskite material may be produced according to themethod described above using this thin film precursor solution. Theaddition of cesium ions through the CsI solution as described above maycause chloride anions and cesium atoms to incorporate into the FAPbI₃crystal lattice. This may result in a greater degree of latticecontraction compared to addition of cesium or rubidium ions as describedabove without addition of chloride ions. Table 1 below shows latticeparameters for FAPbI₃ perovskite materials with 10 mol % rubidium and 20mol % chloride (e.g. 10 mol % PbCl₂), 10 mol % cesium, and 10 mol %cesium with 20 mol % chloride, wherein the mol % concentrationrepresents the concentration of the additive with respect to the leadatoms in the lead halide solution. As can be seen in Table 1, the FAPbI₃perovskite material with cesium and chloride added has smaller latticeparameters than the other two perovskite material samples.

TABLE 1 (001) (002) Sample Details d-spacing d-spacing 10 mol % Rbl +6.3759(15) 3.1822(5) 10 mol % PbCl₂ 10 mol % Csl + 6.3425(13) 3.1736(8)0 mol % PbCl₂ 10 mol % Csl + 6.3272(13) 3.1633(4) 10 mol % PbCl₂

Additionally, data shows that the FAPbI₃ perovskite material withrubidium, cesium and/or chloride added has a Pm3-m cubic structure.FAPbI₃ perovskites with up to and including 10 mol % Rb and 10 mol % Cl,or 10 mol % Cs, or 10 mol % Cs and 10 mol % Cl have been observed tomaintain a cubic Pm3-m cubic crystal structure. FIG. 29 shows x-raydiffraction patterns corresponding to each of the samples presented inTable 1. Tables 2-4 provide the x-ray diffraction peaks and intensityfor the three perovskite materials shown in Table 1. The data werecollected at ambient conditions on a Rigaku Miniflex 600 using a Cu Kαradiation source at a scan rate of 1.5 degrees 2θ/min.

TABLE 2 10 mol % Rbl + 10 mol % PbCl2 2-theta d Height Peak Identity(deg) (ang.) (cps) (phase, miller index) Pbl2, (001) 13.878(3) 6.3759(15) 12605(126)  Perovskite, (001) 19.707(15) 4.501(3) 489(25)Perovskite, (011) 21.320(14) 4.164(3) 286(19) ITO, (112) 24.227(19)3.671(3) 1022(36)  Perovskite, (111) 28.017(4)  3.1822(5)  5683(84) Perovskite, (002) 30.13(4) 2.964(4) 344(21) ITO, (112) 31.403(14)2.8464(13) 913(34) Perovskite, (012)

TABLE 3 10 mol % Csl & 0 mol % PbCl2 2-theta d Height Peak Identity(deg) (ang.) (cps) phase (miller index) 12.614(14) 7.012(8)  99(11)Pbl2, (001) 13.952(3)  6.3425(13) 4921(78)  Perovskite, (001) 19.826(12)4.475(3) 392(22) Perovskite, (011) 21.274(14) 4.173(3) 281(19) ITO,(112) 24.333(15) 3.655(2) 1031(36)  Perovskite, (111) 28.094(7) 3.1736(8)  2332(54)  Perovskite, (002) 30.15(4) 2.962(4) 364(21) ITO,(112) 31.531(12) 2.8351(10) 941(34) Perovskite, (012)

TABLE 4 10 mol % Csl & 10 mol % PbCl2 2-theta d Height Peak Identity(deg) (ang.) (cps) phase (miller index) 12.635(6)  7.000(3) 395(22)Pbl2, (001) 13.985(3)  6.3272(13) 13692(131)  Perovskite, (001)19.867(11) 4.465(2) 807(32) Perovskite, (011) 21.392(13) 4.150(2)254(18) ITO, (112) 24.41(2) 3.643(3) 918(34) Perovskite, (111)28.188(4)  3.1633(4)  6797(92)  Perovskite, (002) 30.14(4) 2.963(4)348(21) ITO, (112) 31.633(15) 2.8262(13) 1027(36)  Perovskite, (012)

A geometrically expected x-ray diffraction pattern for cubic Pm3-mmaterial with a lattice constant=6.3375 Å under Cu-Kα radiation is shownin Table 5. As can be seen from the data, the perovskite materialsproduced with 10 mol % Rb and 10 mol % Cl, 10 mol % Cs, and 10% Cs and10% Cl each have diffraction patterns conforming to the expected patternfor a cubic, Pm3-m perovskite material.

TABLE 5 Geometrically Expected Diffraction Pattern for Cubic Pm3-m,lattice constant = 6.3375 Å; Cu-Kα Radiation) 2-Theta (degrees)d-spacing (angstroms) Miller Index 13.963 6.3375 (0 0 1) 19.796 4.4813(0 1 1) 24.306 3.659 (1 1 1) 28.138 3.1688 (0 0 2) 31.541 2.8342 (0 1 2)

Enhanced Perovskite

So-called “layered” 2D perovskites are known to form when perovskitesare formulated with organic cations having alkyl chains longer than themethylammonium and formamidinium cations described previously herein.Layered 2D perovskites include structures such as the Ruddlesden-Popperphase, Dion-Jacobson phase, and Aurivillius phase. For example, bysubstituting 1-butylammonium in place of the methylammonium or the othercations described above, during formation of a perovskite in a“one-step” method (not described herein), a Ruddlesden-Popper 2Dperovskite may result. In such perovskites the 1-butylammonium preventsthe perovskite from forming a full crystalline lattice, and insteadcauses the perovskite to form in “sheets” of perovskite having a singlecrystal structure in thickness. FIG. 5 illustrates a structure of aRuddlesden-Popper perovskite 5500 with a 1-butylammonium cation 5510. Ascan be seen from FIG. 5, the “tails” of the butylammonium cation 5510result in a separation between the lead and iodide portion of theperovskite material and other lead and iodide structures, resulting in“sheets” of 2D perovskites. Accordingly, introduction of “bulky organic”cations, such as 1-butylammonium or benzylammonium during formation of aperovskite material may be undesirable if the Ruddlesden-Popper form ofthe perovskite is not desired.

However, addition of a dilute amount of 1-butylammonium solution priorto annealing the perovskite material may result in a perovskite as shownin FIG. 6. FIG. 6 illustrates an embodiment of a perovskite material2000 with addition of an alkyl ammonium cation for surface passivation.In the illustrated embodiment, the surface of a formamidinium leadiodide (FAPbI₃) perovskite material 2010 is shown with 1-butylammoniumcation 2020 at the surface. The 1-butylammonium cation, or other “bulky”organic cations as described herein, may diffuse into the perovskitematerial near the surface of the perovskite material crystal lattice, insome embodiments. In particular embodiments, the 1-butylammonium cation,or other “bulky” organic cations as described herein, may reside 50 nmor less into the perovskite material from the crystal lattice surfacesor grain boundaries. The inclusion of “bulky” organic cations, such as1-butylammonium, near or at the surface of a perovskite material mayresult in the formula of the perovskite material deviating from the“ideal” stoichiometry of perovskite materials disclosed herein. Forexample, inclusion of such organic cations may cause the perovskitematerial to have a formula that is either substoichiometric orsuperstoichiometric with respect to the CMX₃ formula described herein.In this case, the general formula for the perovskite material may beexpressed as C_(x)M_(y)X_(z), where x, y and z are real numbers. In someembodiments, a perovskite material may have the formulaC′₂C_(n-1)M_(n)X_(3n+1), where n is an integer. For example, when n=1the perovskite material may have the formula C′₂MX₄, when n=2 theperovskite material may have the formula C′₂CM₂X₇, when n=3 theperovskite material may have the formula C′₂C₂M₃X₁₀, when n=4 theperovskite material may have the formula C′₂C₃M₄X₁₃, and so on. Asillustrated by FIG. 30, the n-value indicates the thickness of aninorganic metal halide sublattice of the perovskite material. A phase ofthe perovskite material having the formula C′₂C_(n-1)M_(n)X_(3n+1), mayform in regions where a bulky organic cation has diffused into, orotherwise entered into, the crystal lattice of a perovskite material.For example, such a phase may be present within 50 nanometers of acrystal lattice surface (e.g. a surface or grain boundary) of aperovskite material that has been formed including a bulky organiccation as disclosed herein.

The carbon “tails” of the 1-butyl ammonium ion may provide a protectiveproperty to the surface of the perovskite by effectively keeping othermolecules away from the surface. In some embodiments, the alkyl group“tail” of the 1-butyl ammonium ion may be oriented away from or parallelto the surface of the perovskite material. In particular, the1-butylammonium “tails” have hydrophobic properties, which preventswater molecules from contacting the surface of the perovskite andprotects the surface of the perovskite material 2010 from water in theenvironment. Additionally, the 1-butylammonium cations may also act topassivate the surface and any grain boundaries or defects with theperovskite material 2010. Passivation refers to an electricalcharacteristic that prevents charge accumulation or “trap states” at thesurface or grain boundaries of the perovskite material 2010. By actingto passivate portions of perovskite material 2010 the 1-butylammoniummay facilitate improved charge transfer in and out of the perovskitematerial 2010 and improve the electrical properties of the photoactivelayer.

In some embodiments, other organic cations may be applied in place of,or in combination with, 1-butylammonium. Examples of other “bulkyorganic” organic cations that may act as to surface passivate perovskitematerial, include, but are not limited to, ethylammonium,propylammonium, n-butylammonium; perylene n-butylamine-imide;butane-1,4-diammonium; 1-pentylammonium; 1-hexylammonium;poly(vinylammonium); phenylethylammonium; benzylammonium;3-phenyl-1-propylammonium; 4-phenyl-1-butylammonium;1,3-dimethylbutylammonium; 3,3-dimethylbutylammonium; 1-heptylammonium;1-octylammonium; 1-nonylammonium; 1-decylammonium; and 1-icosanylammonium. Additionally, bulky organic cations with a tail that containsone or more heteroatoms in addition to the cationic species, theheteroatom may coordinate with, bind to, or integrate with theperovskite material crystal lattice. A heteroatom may be any atom in thetail that is not hydrogen or carbon, including nitrogen, sulfur, oxygen,or phosphorous.

Other examples of “bulky” organic cations may include the followingmolecules functionalized with an ammonium group, phosphonium group, orother cationic group that may integrate into a surface “C-site of aperovskite material: benzene, pyridine, naphthalene, anthracene,xanthene, phenathrene, tetracene chrysene, tetraphene,benzo[c]phenathrene, triphenylene, pyrene, perylene, corannulene,coronene, substituted dicarboxylic imides, aniline,N-(2-aminoethyl)-2-isoindole-1,3-dione, 2-(1-aminoethyl)naphthalene,2-triphenylene-O-ethylamine ether, benzylamine, benzylammonium salts,N-n-butyl-N′-4-aminobutylperylene-3,4,9,10-bis(dicarboximide),1-(4-alkylphenyl)methanamine, 1-(4-alkyl-2-phenyl)ethanamine,1-(4-alkylphenyl)methanamine, 1-(3-alkyl-5-alkylphenyl)methanamine,1-(3-alkyl-5-alkyl-2-phenyl)ethanamine, 1-(4-alkyl-2-phenyl)ethanamine,2-Ethylamine-7-alkyl-Naphthalene, 2-Ethylamine-6-alkyl-Naphthalene,1-Ethylamine-7-alkyl-Naphthalene, 1-Ethylamine-6-alkyl-Naphthalene,2-Methylamine-7-alkyl-Naphthalene, 2-Methylamine-6-alkyl-Naphthalene,1-Methylamine-7-alkyl-Naphthalene, 1-Methylamine-6-alkyl-Naphthalene,N-n-aminoalkyl-N′-4-aminobutylperylene-3,4,9,10-bis(dicarboximide),1-(3-Butyl-5-methoxybutylphenyl)methanamine,1-(4-Pentylphenyl)methanamine,1-[4-(2-Methylpentyl)-2-phenyl]ethanamine,1-(3-Butyl-5-pentyl-2-phenyl)ethanamine,2-(5-[4-Methylpentyl]-2-naphthyl)ethanamine,N-7-tridecyl-N′-4-aminobutylperylene-3,4,9,10-bis(dicarboximide),N-n-heptyl-N′-4-aminobutylperylene-3,4,9,10-bis(dicarboximide),2-(6-[3-Methoxylpropyl]-2-naphthyl)ethanamine. FIGS. 17-28 provideillustrations of the structures of these organic molecules, according tocertain embodiments. With respect to FIGS. 17 and 18, each “R-group,”R_(x) may be any of H, R′, Me, Et, Pr, Ph, Bz, F, Cl, Br, I, NO₂, OR′,NR′₂, SCN, CN, N₃, SR′, where R′ may be any alkyl, alkenyl, or alkynylchain. Additionally, at least one of the illustrated R_(x) groups may be(CH₂)_(n)EX_(y) or (CH₂)_(n)C(EX_(y))₂ where n and y=0, 1, 2, orgreater, n and y may or may not be equal, E is selected from the groupconsisting of C, Si, O, S, Se, Te, N, P, As, or B, and X is a halide orpseudohalide such as F, Cl, Br, I, CN, SCN, or H. Further, with respectto FIG. 19, the illustrated molecules may include any hydrohalide ofeach illustrated amine, for example benzylammonium salts, where theillustrated X group may be F, Cl, Br, I, SCN, CN, or any otherpseudohalide. Other non-halide acceptable anions may include: nitrate,nitrite, carboxylate, acetate, acetonyl acetonate, formate, oxalate,sulfate, sulfite, thiosulfate, phosphate, tetrafluoroborate,hexafluorophosphate, tetra(perfluorophenyl) borate, hydride, oxide,peroxide, hydroxide, nitride, arsenate, arsenite, perchlorate,carbonate, bicarbonate, chromate, dichromate, iodate, bromate, chlorate,chlorite, hypochlorite, hypobromite, cyanide, cyanate, isocyanate,fulminate, thiocyanate, isothiocyanate, azide, tetracarbonylcobaltate,carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide,tricyanomethanide, amide, and permanganate. Suitable R groups may alsoinclude, but are not limited to: hydrogen, methyl, ethyl, propyl, butyl,pentyl group or isomer thereof, any alkane, alkene, or alkyne CxHy,where x=1-20, y=1-42, cyclic, branched or straight-chain; alkyl halides,CxHyXz, x=1-20, y=0-42, z=1-42, X═F, Cl, Br, or I; any aromatic group(e.g., phenyl, alkylphenl, alkoxyphenyl, pyridine, naphthalene); cycliccomplexes where at least one nitrogen is contained within the ring(e.g., pyridine, pyrrole, pyrrolidine, piperidine, tetrahydroquinoline);any sulfur-containing group (e.g., sulfoxide, thiol, alkyl sulfide); anynitrogen-containing group (nitroxide, amine); any phosphorous containinggroup (phosphate); any boron-containing group (e.g., boronic acid); anyorganic acid (e.g., acetic acid, propanoic acid); and ester or amidederivatives thereof, any amino acid (e.g., glycine, cysteine, proline,glutamic acid, arginine, serine, histidine, 5-ammoniumvaleric acid)including alpha, beta, gamma, and greater derivatives; any siliconcontaining group (e.g., siloxane); and any alkoxy or group, —OCxHy,where x=0-20, y=1-42.

Additionally, in some embodiments, the bulky organic cation maypassivate grain boundaries and surface defects in the perovskitematerial. FIG. 7 illustrates an example embodiment of a perovskitematerial layer 3000 with 1-butylammonium 3020 passivating both thesurface and grain boundaries 3015 of a bulk perovskite material 3010. Asdescribed above, the alkyl tails of these ions may also form ahydrophobic layer which repels water and other polar species and impedessuch species from reaching the surface of the perovskite material. Ascan be seen in FIG. 7, the “tails” of the bulky organic cations may notbe chemically connected (e.g., covalently or ionically bonded) to thesurface or grain boundaries 3015 of the perovskite material layer 3000.As used herein, “tails” of any bulky organic cation refers to thenon-ionic carbon structure of the bulky organic cation. For example, thetail of 1-butylammonium is the butyl group and the tail ofbenzylammonium is the benzyl group.

The tails of the bulky organic cation may also assume other arrangementswith respect to the surface or grain boundary of a perovskite material.Generally, the cationic “head” of a bulky organic cation will notdiffuse more than 50 nanometers past the surface or a grain boundary ofa perovskite material. The tail may interact weakly with the perovskitematerial and be oriented away from the perovskite material crystal grainsurface. The tail may have an intermolecular interaction (e.g.,dipole-dipole or hydrogen bonding) with the perovskite material crystalgrain surface resulting in a configuration where the tail is orientedtowards the perovskite material crystal grain surface. In someembodiments, the tails of some bulky organic cations present in theperovskite material may not interact with the surfaces or grainboundaries of the perovskite material and the tails of other bulkyorganic cations in the perovskite material may interact with thesurfaces or grain boundaries of the perovskite material. The tail maycontain a heteroatom or anion (i.e., a zwitterion) with at least oneelectron lone pair that may interact covalently (e.g., a coordinationcovalent bond) with the perovskite material crystal grain surface via ametal atom (e.g., Pb, Sn, Ge, In, Bi, Cu, Ag, Au) present in theperovskite material. The tail may also include a cationic species, suchas diammonium butane as described herein, that may incorporate into theperovskite material by substituting on at least two “C” cation sites(such as formamidinium). A tail including a cationic species may alsobridge two layers of a 2D perovskite material, lie prone across theperovskite material crystal grain surface, or orient away from theperovskite material crystal grain surface in a similar manner to thatdescribed with respect to a non-ionic tail. In another embodiment, abulky organic cation having a sufficiently bulky tail, such as animidazolium cation, may simply reside on the perovskite surface or grainboundary without diffusing into the perovskite material.

Additionally, in other embodiments, the bulky organic cations with tailgroups that vary in length or size may be applied to the perovskite topassivate grain boundaries and surface defects in the perovskitematerial. FIG. 8 illustrates an example embodiment of a perovskitematerial layer 4000 with a combination of 1-butylammonium 4020,1-nonylammonium 4021, 1-heptylammonium 4022, and 1-hexyl ammonium 4023passivating both the surface and grain boundaries 4015 of a bulkperovskite material 4010. In particular embodiments, any mixture of thealkylammonium compounds identified above may be applied to a perovskitematerial as described herein. FIG. 8 illustrates an example embodimentof a perovskite material layer 4000 with a combination of1-butylammonium 4020, 1-nonylammonium 4021, 1-heptylammonium 4022, and1-hexyl ammonium 4023 passivating both the surface and grain boundaries4015 of a bulk perovskite material 4010. In particular embodiments, anymixture of the alkylammonium compounds identified above may be appliedto a perovskite material as described herein. In some embodiments bulkyorganic cations may include a benzyl group. FIG. 8A illustrates anexample embodiment of a perovskite material layer 4500 with a variety ofbulky organic cations containing benzyl groups passivating both thesurface and grain boundaries 4515 of a bulk perovskite material 4510.

Addition of a 1-butylammonium surface coating to a perovskite materialas described above has been shown to increase the high temperaturedurability of the perovskite in damp environments. FIG. 9 shows acomparison of images taken of a perovskite material with and without a1-butylammonium (“BAI”) surface coating over a period of 48 days. Bothperovskite materials had the same composition and were exposed to anenvironment having a temperature of 85° C. at 55% relative humidity for48 days. As can be seen from the photographs, the perovskite materialhaving no 1-butylammonium surface coating lightens in colorsignificantly after one day of exposure to the environment, indicatingthat the perovskite material has degraded significantly. The perovskitematerial having the 1-butylammonium surface coating shows a graduallightening of color over 48 days and remains partially dark after 48days. This indicates that the perovskite material with the1-butylammonium surface coating is more robust than a perovskitematerial without a 1-butylammonium surface coating during extendedexposure to a high-temperature environment.

FIG. 10 shows a comparison of images taken of a perovskite material withand without a 1-butylammonium (“BAI”) surface coating over a period ofseven days. Both perovskite materials had the same composition and wereexposed to an environment having a temperature of 85° C. at 0% relativehumidity for 7 days. As can be seen from the photographs, the perovskitematerial having no 1-butylammonium surface coating lightens in colorsignificantly after one day of exposure to the environment, indicatingthat the perovskite material has degraded significantly. The perovskitematerial having the 1-butylammonium surface coating shows very littlechange in color after seven days. This indicates that the perovskitematerial with the 1-butylammonium surface coating did not completelybreak down during extended exposure to a high-temperature, high-humidityenvironment.

In other embodiments, perylene n-butylamine-imide may be applied to thesurface of a perovskite material as described above with respect to1-butylammonium. FIGS. 11A-D illustrate various perylene monoimides anddiimides that may be applied to the surface of a perovskite materialaccording to the present disclosure. FIG. 12 illustrates an embodimentof a perovskite material 2500 with addition of an alkyl ammonium cationfor surface passivation. In the illustrated embodiment, the surface of aformamidinium lead iodide (FAPbI₃) perovskite material 2510 is shownwith perylene n-butylamine-imide 2520 at the surface. As with the1-butylammonium illustrated in FIG. 6, the carbon “tails” of theperylene n-butylamine-imide ion may provide a protective property to thesurface of the perovskite by effectively keeping other molecules awayfrom the surface. In particular, the perylene n-butylamine-imide “tails”have hydrophobic properties, which prevents water molecules fromcontacting the surface of the perovskite and protects the surface of theperovskite material 2510 from water in the environment. Additionally,the perylene n-butylamine-imide cations may also act to passivate thesurface and any grain boundaries or defects with the perovskite material2510. By acting to passivate portions of perovskite material 2510 theperylene n-butylamine-imide may facilitate improved charge transfer inand out of the perovskite material 2510 and improve the electricalproperties of the photoactive layer.

An example method for depositing the 1-butylammonium prior to annealingthe perovskite material is described below.

First, a lead halide precursor ink is formed. An amount of lead halidemay be massed in a clean, dry vessel in a controlled atmosphereenvironment (e.g., controlled atmosphere box with glove-containingportholes allows for materials manipulation in an air-free environment).Suitable lead halides include, but are not limited to, lead (II) iodide,lead (II) bromide, lead (II) chloride, and lead (II) fluoride. The leadhalide may comprise a single species of lead halide or it may comprise alead halide mixture in a precise ratio. In certain embodiments, the leadhalide mixture may comprise any binary, ternary, or quaternary ratio of0.001-100 mol % of iodide, bromide, chloride, or fluoride. In oneembodiment, the lead halide mixture may comprise lead (II) chloride andlead (II) iodide in a ratio of about 10:90 mol:mol. In otherembodiments, the lead halide mixture may comprise lead (II) chloride andlead (II) iodide in a ratio of about 5:95, about 7.5:92.5, or about15:85 mol:mol.

Alternatively, other lead salt precursors may be used in conjunctionwith or in lieu of lead halide salts to form the precursor ink. Suitableprecursor salts may comprise any combination of lead (II) or lead(IV)and the following anions: nitrate, nitrite, carboxylate, acetate,acetonyl acetonate, formate, oxalate, sulfate, sulfite, thiosulfate,phosphate, tetrafluoroborate, hexafluorophosphate,tetra(perfluorophenyl) borate, hydride, oxide, peroxide, hydroxide,nitride, arsenate, arsenite, perchlorate, carbonate, bicarbonate,chromate, dichromate, iodate, bromate, chlorate, chlorite, hypochlorite,hypobromite, cyanide, cyanate, isocyanate, fulminate, thiocyanate,isothiocyanate, azide, tetracarbonylcobaltate,carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide,tricyanomethanide, amide, and permanganate.

The precursor ink may further comprise a lead (II) or lead (IV) salt inmole ratios of 0 to 100% to the following metal ions Be, Mg, Ca, Sr, Ba,Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, In, Tl, Sb, Bi, Ti, Zn, Cd,Hg, and Zr as a salt of the aforementioned anions.

A solvent may then be added to dissolve the lead solids to form the leadhalide precursor ink. Suitable solvents include, but are not limited to,dry N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide,dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol, propanol,butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine,alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene,dichloromethane, chloroform, alkylnitrile, arylnitrile, acetonitrile,alkoxylalcohols, alkoxyethanol, 2-methoxyethanol, glycols, propyleneglycol, ethylene glycol, and combinations thereof. In one embodiment,the lead solids are dissolved in dry dimethylformamide (DMF). The leadsolids may be dissolved at a temperature between about 20° C. to about150° C. In some embodiments, the solvent may further comprise2-methoxyethanol and acetonitrile. In some embodiments, 2-methoxyethanoland acetonitrile may be added in a volume ratio of from about 25:75 toabout 75:25, or at least 25:75. In certain embodiments, the solvent mayinclude a ratio of 2-methoxyethanol and acetonitrile to DMF of fromabout 1:100 to about 1:1, or from about 1:100 to about 1:5, on a volumebasis. In certain embodiments, the solvent may include a ratio of2-methoxyethanol and acetonitrile to DMF of at least about 1:100 on avolume basis. In one embodiment, the lead solids are dissolved at about85° C. The lead solids may be dissolved for as long as necessary to forma solution, which may take place over a time period up to about 72hours. The resulting solution forms the base of the lead halideprecursor ink. In some embodiments, the lead halide precursor ink mayhave a lead halide concentration between about 0.001M and about 10M. Inone embodiment, the lead halide precursor ink has a lead halideconcentration of about 1 M.

Optionally, certain additives may be added to the lead halide precursorink to affect the final perovskite crystallinity and stability. In someembodiments, the lead halide precursor ink may further comprise an aminoacid (e.g., 5-aminovaleric acid, histidine, glycine, lysine), an aminoacid hydrohalide (e.g., 5-amino valeric acid hydrochloride), an IFLsurface-modifying (SAM) agent (such as those discussed earlier in thespecification), or a combination thereof. In one embodiment,formamidinium chloride may be added to the lead halide precursor ink. Inother embodiments, the halide of any cation discussed earlier in thespecification may be used. In some embodiments, combinations ofadditives may be added to the lead halide precursor ink including, forexample, the combination of formamidinium chloride and 5-amino valericacid hydrochloride.

The additives, including formamidinium chloride and/or 5-amino valericacid hydrochloride may be added to the lead halide precursor ink atvarious concentrations depending on the desired characteristics of theresulting perovskite material. In one embodiment, the additives may beadded in a concentration of about 1 nM to about 1 M. In anotherembodiment, the additives may be added in a concentration of about 1 μMto about 1 M. In another embodiment, the additives may be added in aconcentration of about 1 μM to about 1 mM.

In some embodiments, a Group 1 metal halide solution is formed to beadded to the lead halide precursor ink. An amount of Group 1 metalhalide may be massed in a clean, dry vessel in a controlled atmosphereenvironment. Suitable Group 1 metal halides include, but are not limitedto, cesium iodide, cesium bromide, cesium chloride, cesium fluoride,rubidium iodide, rubidium bromide, rubidium chloride, rubidium fluoride,lithium iodide, lithium bromide, lithium chloride, lithium fluoride,sodium iodide, sodium bromide, sodium chloride, sodium fluoride,potassium iodide, potassium bromide, potassium chloride, potassiumfluoride. The Group 1 metal halide may comprise a single species ofGroup 1 metal halide or it may comprise a Group 1 metal halide mixturein a precise ratio. In one embodiment the Group 1 metal halide maycomprise cesium iodide. In another embodiment the Group 1 metal halidemay comprise rubidium iodide. In another embodiment the Group 1 metalhalide may comprise sodium iodide. In another embodiment the Group 1metal halide may comprise potassium iodide.

Alternatively, other Group 1 metal salt precursors may be used inconjunction with or in lieu of Group 1 metal halide salts to form aGroup 1 metal salt solution. Suitable precursor Group 1 metal salts maycomprise any combination of Group 1 metals and the following anions:nitrate, nitrite, carboxylate, acetate, formate, oxalate, sulfate,sulfite, thiosulfate, phosphate, tetrafluoroborate, hexafluorophosphate,tetra(perfluorophenyl) borate, hydride, oxide, peroxide, hydroxide,nitride, arsenate, arsenite, perchlorate, carbonate, bicarbonate,chromate, dichromate, iodate, bromate, chlorate, chlorite, hypochlorite,hypobromite, cyanide, cyanate, isocyanate, fulminate, thiocyanate,isothiocyanate, azide, tetracarbonylcobaltate,carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide,tricyanomethanide, amide, and permanganate.

A solvent may then be added to the vessel to dissolve the Group 1 metalhalide solids to form the Group 1 metal halide solution. Suitablesolvents include, but are not limited to, dryN-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide(DMF), dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol,propanol, butanol, tetrahydrofuran, formamide, tert-butylpyridine,pyridine, alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene,dichloromethane, chloroform, and combinations thereof. In oneembodiment, the lead solids are dissolved in dry dimethylsulfoxide(DMSO). The Group 1 metal halide solids may be dissolved at atemperature between about 20° C. to about 150° C. In one embodiment, theGroup 1 metal halide solids are dissolved at room temperature (i.e.about 25° C.). The Group 1 metal halide solids may be dissolved for aslong as necessary to form a solution, which may take place over a timeperiod up to about 72 hours. The resulting solution forms the Group 1metal halide solution. In some embodiments, the Group 1 metal halidesolution may have a Group 1 metal halide concentration between about0.001M and about 10M. In one embodiment, the Group 1 metal halidesolution has a Group 1 metal halide concentration of about 1 M. In someembodiments, the Group 1 metal halide solution may further comprise anamino acid (e.g., 5-aminovaleric acid, histidine, glycine, lysine), anamino acid hydrohalide (e.g., 5-amino valeric acid hydrochloride), anIFL surface-modifying (SAM) agent (such as those discussed earlier inthe specification), or a combination thereof.

Next, the lead halide solution and the Group 1 metal halide solution aremixed to form a thin-film precursor ink. The lead halide solution andGroup 1 metal halide solution may be mixed in a ratio such that theresulting thin-film precursor ink has a molar concentration of the Group1 metal halide that is between 0% and 25% of the molar concentration ofthe lead halide. In particular embodiments, the thin-film precursor inkmay have a molar concentration of the Group 1 metal halide that is 1% ofthe molar concentration of the lead halide. In particular embodiments,the thin-film precursor ink may have a molar concentration of the Group1 metal halide that is 5% of the molar concentration of the lead halide.In particular embodiments, the thin-film precursor ink may have a molarconcentration of the Group 1 metal halide that is 10% of the molarconcentration of the lead halide. In particular embodiments, thethin-film precursor ink may have a molar concentration of the Group 1metal halide that is 15% of the molar concentration of the lead halide.In particular embodiments, the thin-film precursor ink may have a molarconcentration of the Group 1 metal halide that is 20% of the molarconcentration of the lead halide. In particular embodiments, thethin-film precursor ink may have a molar concentration of the Group 1metal halide that is 25% of the molar concentration of the lead halide.In some embodiments the lead halide solution and the Group 1 metalhalide solution may be stirred or agitated during or after mixing.

Optionally, in certain embodiments, water may be added to the leadhalide precursor ink. In some embodiments, the solvent may furthercomprise 2-methoxyethanol and acetonitrile. In some embodiments,2-methoxyethanol and acetonitrile may be added in a volume ratio of fromabout 25:75 to about 75:25, or at least 25:75. In certain embodiments,the solvent may include a ratio of 2-methoxyethanol and acetonitrile toDMF of from about 1:100 to about 1:1, or from about 1:100 to about 1:5,on a volume basis. In certain embodiments, the solvent may include aratio of 2-methoxyethanol and acetonitrile to DMF of at least about1:100 on a volume basis. By way of explanation, and without limiting thedisclosure to any particular theory or mechanism, the presence of wateraffects perovskite thin-film crystalline growth. Under normalcircumstances, water may be absorbed as vapor from the air. However, itis possible to control the perovskite PV crystallinity through thedirect addition of water to the lead halide precursor ink in specificconcentrations. Suitable water includes distilled, deionized water, orany other source of water that is substantially free of contaminants(including minerals). It has been found, based on light I-V sweeps, thatthe perovskite PV light-to-power conversion efficiency may nearly triplewith the addition of water compared to a completely dry device.

The water may be added to the lead halide precursor ink at variousconcentrations depending on the desired characteristics of the resultingperovskite material. In one embodiment, the water may be added in aconcentration of about 1 nL/mL to about 1 mL/mL. In another embodiment,the water may be added in a concentration of about 1 μL/mL to about 0.1mL/mL. In another embodiment, the water may be added in a concentrationof about 1 μL/mL to about 20 μL/mL.

The lead halide precursor ink or the thin film precursor ink may then bedeposited on the desired substrate. Suitable substrate layers mayinclude any of the substrate layers identified earlier in thisdisclosure. As noted above, the lead halide precursor ink or the thinfilm precursor ink may be deposited through a variety of means,including but not limited to, drop casting, spin casting, blade coating,slot-die printing, screen printing, or ink-jet printing. In certainembodiments, the lead halide precursor ink or the thin film precursorink may be spin-coated onto the substrate at a speed of about 500 rpm toabout 10,000 rpm for a time period of about 5 seconds to about 600seconds. In one embodiment, the lead halide precursor ink or the thinfilm precursor ink may be spin-coated onto the substrate at about 3000rpm for about 30 seconds. In some embodiments, multiple subsequentdepositions of the precursor ink may be made to form a thin-film layer.The lead halide precursor ink or the thin film precursor ink may bedeposited on the substrate at an ambient atmosphere in a humidity rangeof about 0% relative humidity to about 50% relative humidity. The leadhalide precursor ink or the thin film precursor ink may then be allowedto dry in a substantially water-free atmosphere, i.e., less than 30%relative humidity, to form a thin film.

After deposition of the lead halide precursor or thin film precursor, abulky organic cation as described above (e.g. benzylammonium,phenylethylammonium, ethylammonium, propylammonium, n-butylammonium;butane-1,4-diammonium; 1-pentylammonium; 1-hexylammonium;poly(vinylammonium); phenylethylammonium; 3-phenyl-1-propylammonium;4-phenyl-1-butylammonium; 1,3-dimethylbutylammonium;3,3-dimethylbutylammonium; 1-heptylammonium; 1-octylammonium;1-nonylammonium; 1-decylammonium; 1-icosanyl ammonium; or any otherbulky cation described herein or illustrated in FIGS. 17-28) saltsolution may be applied to the thin film resulting from the depositionof the lead salt precursor and the second salt precursor. Bulky organicsalts may include halide, nitrate, nitrite, carboxylate, acetate,acetonyl acetonate, formate, oxalate, sulfate, sulfite, thiosulfate,phosphate, tetrafluoroborate, hexafluorophosphate,tetra(perfluorophenyl) borate, hydride, oxide, peroxide, hydroxide,nitride, arsenate, arsenite, perchlorate, carbonate, bicarbonate,chromate, dichromate, iodate, bromate, chlorate, chlorite, hypochlorite,hypobromite, cyanide, cyanate, isocyanate, fulminate, thiocyanate,isothiocyanate, azide, tetracarbonylcobaltate,carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide,tricyanomethanide, amide, and/or permanganate salts of any of thepreceding cations. The bulky organic cation salt solution may be formedby dissolving a bulky organic cation salt in a solvent such as analcohol, dry N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone,dimethylformamide (DMF), dialkylformamide, dimethylsulfoxide (DMSO),methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide,tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene,dichlorobenzene, dichloromethane, chloroform, and combinations thereof.In a particular embodiment, the bulky organic cation salt may bedissolved in isopropyl alcohol. In certain embodiments, the bulkyorganic cation salt solution may have a concentration between 0.0001 Mand 1.0 M of the bulky organic cation salt. In other embodiments, thebulky organic cation salt solution may have a concentration between 0.01M and 0.1 M of the bulky organic cation salt. In particular embodiments,the bulky organic cation salt solution may have a concentration ofbetween 0.02 and 0.05 M of the bulky organic cation salt. In aparticular embodiment, the bulky organic cation salt solution may have aconcentration of approximately 0.05 M of the bulky organic cation salt.The bulky organic cation salt solution may be deposited onto theperovskite material precursor thin film by any method described hereinwith respect to solution deposition. These methods may include, spraycoating, drop casting, spin casting, blade coating, slot-die printing,screen printing, gravure printing, or ink-jet printing. In oneembodiment, the bulky organic cation salt may be 1-butylammonium iodide.In another embodiment, the bulky organic cation salt may bebenzylammonium iodide. In yet another embodiment, the bulky organiccation salt may be phenylethylammonium iodide.

The thin film may then be thermally annealed for a time period up toabout 24 hours at a temperature of about 20° C. to about 300° C. In oneembodiment, the thin film may be thermally annealed for about tenminutes at a temperature of about 50° C. The perovskite material activelayer may then be completed by a conversion process in which theprecursor film is submerged or rinsed with a solution comprising asolvent or mixture of solvents (e.g., DMF, isopropanol, methanol,ethanol, butanol, chloroform chlorobenzene, dimethylsulfoxide, water)and salt (e.g., methylammonium iodide, formamidinium iodide, guanidiniumiodide, 1,2,2-triaminovinylammonium iodide, 5-aminovaleric acidhydroiodide) in a concentration between 0.001M and 10M. In certainembodiments, the thin films may also be thermally post-annealed in thesame fashion as in the first line of this paragraph.

After the thin film is deposited and, in some embodiments, annealed, asecond salt precursor (e.g., formamidinium iodide, formamidiniumthiocyanate, or guanidinium thiocyanate) may be deposited onto the leadsalt thin film, where the thin film may have a temperature about equalto ambient temperature or have a controlled temperature between 0° C.and 500° C. The second salt precursor may be deposited at ambienttemperature or at elevated temperature between about 25° C. and 125° C.The second salt precursor may be deposited by a variety of methods knownin the art, including but not limited to spin-coating, blade coating,slot-die printing, ink-jet printing, gravure printing, screen printing,sputtering, PE-CVD, thermal evaporation, or spray coating. In someembodiments, multiple subsequent depositions of the second salt solutionmay be made to form a thin-film layer. In some embodiments the secondsalt precursor may be a solution containing one or more solvents. Forexample, the second salt precursor may contain one or more of dryN-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide,dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol, propanol,butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine,alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene,dichloromethane, chloroform, and combinations thereof.

In some embodiments, any bulky organic cation salt as described hereinmay be combined with the second salt solution prior to deposition of thesecond salt solution. In particular embodiments, a bulky organic cationsalt solution may be prepared as described above and mixed with thesecond salt solution prior to deposition of the second salt solution.For example, the bulky organic cation salt solution may have aconcentration between 0.0001 M and 1.0 M of the bulky organic cationsalt. In other embodiments, the bulky organic cation salt solution mayhave a concentration between 0.01 M and 0.1 M of the bulky organiccation salt. In particular embodiments, the bulky organic cation saltsolution may have a concentration of between 0.02 and 0.05 M of thebulky organic cation salt. In a particular embodiment, the bulky organiccation salt solution may have a concentration of approximately 0.05 M ofthe bulky organic cation salt. In other embodiments, a bulky organiccation salt solution may be deposited onto a lead halide thin filmformed after deposition of a lead halide precursor ink or thin filmprecursor ink. In another embodiment, a bulky organic cation saltsolution may be deposited onto a perovskite precursor thin film afterdeposition of the second salt solution.

Finally, the substrate with the perovskite material precursor thin filmmay be annealed. Annealing the substrate may convert the lead saltprecursor and second salt precursor to a perovskite material, (e.g.FAPbI₃, GAPb(SCN)₃, FASnI₃), with a surface passivating layer of thebulky organic cation. Annealing may be performed in a variety ofatmospheres at ambient pressure (e.g. about one atmosphere (760 Torr),depending on elevation and atmospheric conditions) or at pressures lessthan atmospheric or ambient (e.g., 1 mTorr to 500 mTorr). An annealingatmosphere may comprise ambient air, a controlled humidity environment(e.g., 0-100 g H₂O/m³ of gas), pure argon, pure nitrogen, pure oxygen,pure hydrogen, pure helium, pure neon, pure krypton, pure CO₂ or anycombination of the preceding gases. A controlled humidity environmentmay include an environment in which the absolute humidity or the %relative humidity is held at a fixed value, or in which the absolutehumidity or the % relative humidity varies according to predeterminedset points or a predetermined function. In particular embodiments,annealing may occur in a controlled humidity environment having a %relative humidity greater than or equal to 0% and less than or equal to50%. In other embodiments, annealing may occur in a controlled humidityenvironment containing greater than or equal to 0 g H₂O/m³ gas and lessthan or equal to 20 g H₂O/m³ gas. In some embodiments, annealing mayoccur at a temperature greater than or equal to 50° C. and less than orequal to 300° C.

For example, in a particular embodiment, a FAPbI₃ perovskite materialmay be formed by the following process. First a lead (II) halideprecursor comprising about a 90:10 mole ratio of PbI₂ to PbCl₂ dissolvedin anhydrous DMF may be deposited onto a substrate by spin-coating,blade coating, or slot-die printing. The lead halide precursor ink maybe allowed to dry in a substantially water-free atmosphere, i.e., lessthan 30% relative humidity or 17 g H₂O/m³, for approximately one hour(±15 minutes) to form a thin film. The thin film may be subsequentlythermally annealed for about ten minutes at a temperature of about 50°C. (±10° C.). In other embodiments, the lead halide precursor may bedeposited by ink-jet printing, gravure printing, screen printing, bladecoating, sputtering, PE-CVD, atomic-layer deposition, thermalevaporation, or spray coating. Next, a 1-butylammonium salt solutionhaving a concentration of 0.05 M in isopropyl alcohol may be depositedonto the lead halide thin film. Next, a formamidinium iodide precursorcomprising a 15-100 mg/mL concentration of formamidinium iodidedissolved in anhydrous isopropyl alcohol may be deposited onto the leadhalide thin film by spin coating or blade coating. In other embodiments,the formamidinium iodide precursor may be deposited by ink-jet printing,gravure printing, screen printing, slot-die printing, sputtering,PE-CVD, atomic-layer deposition, thermal evaporation, or spray coating.Next, the substrate may be annealed at about 25% relative humidity(about 4 to 7 g H₂O/m³ gas) and between about 100° C. and 200° C. toform a formamidinium lead iodide (FAPbI₃) perovskite material, with asurface layer of 1-butylammonium. In alternative embodiments, the1-butylammonium salt solution may be deposited onto the thin film formedafter deposition of the formamidinium iodide precursor. In anotherembodiment, the 1-butylammonium salt solution may be combined with thelead halide precursor ink prior to deposition of the lead halideprecursor ink. In yet another embodiment, the 1-butylammonium saltsolution may be combined with the formamidinium iodide precursor priorto deposition of the formamidinium iodide precursor. In yet anotherembodiment, the 1-butylammonium salt solution may be deposited onto thethin film following deposition of the formamidinium iodide precursor andprior to annealing the thin film and substrate. In yet anotherembodiment, the 1-butylammonium salt solution may be deposited onto thethin film after annealing the thin film and substrate.

In other embodiments, using the process described above with a lead (II)iodide solution, a cesium iodide solution, a methylammonium (MA) iodidesalt solution, and a 1-butylammonium salt solution may result in aperovskite material having the formula of Cs_(i)MA_(1-i)PbI₃, where iequals a number between 0 and 1 with a surface layer of 1-butylammonium.As another example, the using a lead (II) iodide solution, a rubidiumiodide solution, a formamidinium (FA) iodide salt solution, and a1-butylammonium salt solution may result in a perovskite material havingthe formula of Rb_(i)FA_(1-i)PbI₃, where i equals a number between 0 and1 with a surface layer of 1-butylammonium layer. As another example,using the process described above with a lead (II) iodide solution, acesium iodide solution, a formamidinium (FA) iodide salt solution, and a1-butylammonium salt solution may result in a perovskite material havingthe formula of Cs_(i)FA_(1-i)PbI₃, where i equals a number between 0 and1 with a surface layer of 1-butylammonium layer. As another example, theusing a lead (II) iodide solution, a potassium iodide solution, aformamidinium (FA) iodide salt solution, and a 1-butylammonium saltsolution may result in a perovskite material having the formula ofK_(i)FA_(1-i)PbI₃, where i equals a number between 0 and 1 with asurface layer of 1-butylammonium layer. As another example, the using alead (II) iodide solution, a sodium iodide solution, a formamidinium(FA) iodide salt solution, and a 1-butylammonium salt solution mayresult in a perovskite material having the formula ofNa_(i)FA_(1-i)PbI₃, where i equals a number between 0 and 1 with asurface layer of 1-butylammonium layer. As another example, the using alead (II) iodide-lead (II) chloride mixture solution, a cesium iodidesolution, a formamidinium (FA) iodide salt solution, and a1-butylammonium salt solution may result in a perovskite material havingthe formula of Cs_(i)FA_(1-i)PbI_(3-y)Cl_(y), where i equals a numberbetween 0 and 1 and y represents a number between 0 and 3 with a surfacelayer of 1-butylammonium layer.

In another embodiment, a FAPbI₃ perovskite material may be formed by thefollowing process. First a lead (II) halide precursor ink comprisingabout a 90:10 mole ratio of PbI₂ to PbCl₂ dissolved in anhydrous DMF maybe deposited onto a substrate by spin-coating, blade coating, orslot-die printing. The lead halide precursor ink may be allowed to dryin a substantially water-free atmosphere, i.e., less than 30% relativehumidity or 17 g H₂O/m³, for approximately one hour (±15 minutes) toform a thin film. The thin film may be subsequently thermally annealedfor about ten minutes at a temperature of about 50° C. (±10° C.). Inother embodiments, the lead halide precursor may be deposited by ink-jetprinting, gravure printing, screen printing, sputtering, PE-CVD,atomic-layer deposition, thermal evaporation, or spray coating. Next, aformamidinium iodide precursor comprising a 15-60 mg/mL concentration offormamidinium iodide dissolved in anhydrous isopropyl alcohol may bedeposited onto the lead halide thin film by spin coating or bladecoating. In other embodiments, the formamidinium iodide precursor may bedeposited by ink-jet printing, gravure printing, screen printing,slot-die printing, sputtering, PE-CVD, atomic-layer deposition, bladecoating, thermal evaporation, or spray coating. After depositing thelead halide precursor and formamidinium iodide precursor, abenzylammonium salt solution having a concentration of 0.04 M inisopropyl alcohol may be deposited onto the perovskite materialprecursor thin film. Next, the substrate may be annealed at about 25%relative humidity (about 4 to 7 g H₂O/m³ gas) and between about 100° C.and 200° C. to form a formamidinium lead iodide (FAPbI₃) perovskitematerial, with a surface layer of benzylammonium. In particularembodiments, the benzylammonium salt solution may be deposited onto thelead halide thin film prior to deposition of the formamidinium iodideprecursor. In another embodiment, the benzylammonium salt solution maybe combined with the lead halide precursor ink prior to deposition ofthe lead halide precursor ink. In yet another embodiment, thebenzylammonium salt solution may be combined with the formamidiniumiodide precursor prior to deposition of the formamidinium iodideprecursor. In some embodiments, the resulting perovskite material mayhave a cubic crystal structure in the bulk material away from thesurface. The presence of bulky organic cations near the surface of theperovskite material may result in a non-cubic crystal structure near thesurface of the perovskite material.

In other embodiments, using the process described above with a lead (II)iodide solution, a cesium iodide solution, a methylammonium (MA) iodidesalt solution, and a 1-butylammonium salt solution may result in aperovskite material having the formula of Cs_(i)MA_(1-i)PbI₃, where iequals a number between 0 and 1 with a surface layer of benzylammonium.As another example, using the process described above with a lead (II)iodide solution, a rubidium iodide solution, a formamidinium (FA) iodidesalt solution, and a benzylammonium salt solution may result in aperovskite material having the formula of Rb_(i)FA_(1-i)PbI₃, where iequals a number between 0 and 1 with a surface layer of benzylammoniumlayer. As another example, using the process described above with a lead(II) iodide solution, a cesium iodide solution, a formamidinium (FA)iodide salt solution, and a benzylammonium salt solution may result in aperovskite material having the formula of Cs_(i)FA_(1-i)PbI₃, where iequals a number between 0 and 1 with a surface layer of benzylammoniumlayer. As another example, using the process described above with a lead(II) iodide solution, a potassium iodide solution, a formamidinium (FA)iodide salt solution, and a benzylammonium salt solution may result in aperovskite material having the formula of K_(i)FA_(1-i)PbI₃, where iequals a number between 0 and 1 with a surface layer of benzylammoniumlayer. As another example, using the process described above with a lead(II) iodide solution, a sodium iodide solution, a formamidinium (FA)iodide salt solution, and a benzylammonium salt solution may result in aperovskite material having the formula of Na_(i)FA_(1-i) PbI₃, where iequals a number between 0 and 1 with a surface layer of benzylammoniumr. As another example, using the process described above with a lead(II) iodide-lead (II) chloride mixture solution, a cesium iodidesolution, a formamidinium (FA) iodide salt solution, and abenzylammonium salt solution may result in a perovskite material havingthe formula of Cs_(i)FA_(1-i)Pb_(3-y)Cl_(y), where i equals a numberbetween 0 and 1 and y represents a number between 0 and 3 with a surfacelayer of benzylammonium layer.

A method for producing a perovskite material with benzylammonium isdescribed below. First, a lead iodide precursor ink is prepared bydissolving PbI₂, PbCl₂, and cesium iodide (CsI) in a mixture of DMF andDMSO solvents. To prepare the lead iodide precursor in, a 1.5 M CsI/DMSOsolution is prepared by dissolving CsI in DMSO. The CsI/DMSO solutionmay be prepared, in a particular embodiment, by stirring CsI into DMSOat a ratio of 1.5 mmol of CsI per 1.0 mL of anhydrous DMSO at roomtemperature for between 1 hour and 2.5 hours. Next, the aforementionedCsI solution is added to a solution of PbI₂, PbCl₂, and anhydrous DMFsolvent to form a 1.28 M Pb²⁺ solution in which the ratios of Cs to Pbis 1:10 and the ratio of I to Cl is 9:1. In a particular embodiment, the1.28 M Pb²⁺ solution may be prepared by adding the CsI solution into avessel containing 1.26 mmol of PbI₂, 0.14 mmol of PbCl₂, and 1.0 mL ofanhydrous DMF solvent for each 93.8 μL of the CsI solution. The Pb²⁺solution is mixed at a temperature between 50° C. and 100° C. forbetween 1.5 hour and 2.5 hours before being cooled to form the leadiodide precursor ink. In a particular embodiment, the Pb²⁺ solution maybe stirred at 85° C. for two hours before being cooled by stirring thesolution in a room temperature environment for one hour. In someembodiments, the lead iodide precursor ink may be filtered prior todeposition of the lead iodide precursor ink. A 0.2 μm filter may be usedto filter the lead iodide precursor ink, in a particular embodiment.

Formamidinium iodide (FAI) and benzylammonium iodide (BzAI) solutionsare prepared by dissolving FAI and BzAI salts in anhydrous isopropanol(IPA) to form a 0.2 M FAI solution and 0.05 M BzAI solution,respectively. In particular embodiments, both the FAI and BzAI solutionsmay be held at 75° C. during the following coating process.

Next, the lead iodide precursor ink is deposited onto a substrate andsubsequently annealed to form a lead iodide film. In a particularembodiment, the lead iodide precursor ink held at 45° C. may beblade-coated onto a substrate coated with a nickel oxide (NiO) thin filmlayer and subsequently annealed at 50° C. for 10 minutes to form thelead iodide film.

Next, to form the perovskite material layer, the lead iodide film isfirst underwashed with one coat of the BzAI solution, followed by threecoats of the FAI solution. Following deposition of each of the coats ofBzAI solution and FAI solution, the coat is allowed to dry prior todeposition of the following coating. In particular embodiments, both theBzAI and the FAI solutions may be held at 45° C. during deposition ofeach respective coat. After the third FAI coat has been deposited, thesubstrate and coatings may be annealed to form the perovskite materiallayer. In a particular embodiment, after the third FAI has beendeposited, the substrate is immediately heated to 157° C. for 5 minutesto anneal the perovskite material layer.

The foregoing method may have several advantages. For example,depositing the BzAI solution onto the lead iodide film prior todeposition of the FAI solution may provide intermediate templating forgrowth of the 3D FAPbI₃ perovskite material by formation of a 2Dperovskite material. BzAI may react with lead iodide thin film to forman intermediate 2D perovskite material phase. Upon reacting with FAIafter deposition of the FAI solution, the BzA⁺ cations in the 2D phasemay be fully or partially replaced with FA⁺ cations to form a 3D FAPbI₃framework. Additionally, the BzAI may also passivate crystal defects inthe 3D FAPbI₃ perovskite material. Photoluminescence intensity of FAPbI₃thin films formed by the process described above is brighter (higher)compared to that of FAPbI₃ thin films formed by a process not includingBzAI. FIG. 31 illustrates both optical (absorbance) andphotoluminescence images of a perovskite material photovoltaic device3105 produced without addition of BzAI and perovskite materialphotovoltaic device 3110 produced with BzAI as described herein. FIG. 31shows that the optical image of perovskite material photovoltaic device3110 is darker, indicating a higher light absorbance, and thephotoluminescence image of perovskite material photovoltaic device 3110is brighter than perovskite material photovoltaic device 3105.Additionally, power output has been observed to be greater fromperovskite material photovoltaic devices incorporating BzAI. FIG. 32illustrates power output curve 3205 corresponding to a photovoltaicdevice without BzAI, such as photovoltaic device 3105, and power outputcurve 3210 corresponding to a photovoltaic device with BzAI as describedherein, such as photovoltaic device 3110. The power output measurementsdepicted in FIG. 32 were measured at maximum power point under 100mW/cm² AM1.5G illumination for 180 seconds with an intervening 30 seconddark measurement to demonstrate steady-state performance. As can be seenfrom FIG. 32, a photovoltaic device incorporating BzAI during productionproduces more power per unit area (16.0 mW/cm²) more voltage (785 mV),and more current per unit area (20.3 mA/cm²) than a photovoltaic deviceproduced without BzAI (15.0 mW/cm², 770 mV, and 19.5 mA/cm²). FIG. 33illustrates a current-voltage (I-V) scan 3320 of a perovskite materialphotovoltaic device produced without BzAI, labeled as the sample “5r”line, and a perovskite material photovoltaic device produced with BzAI,labeled as the sample “10r” line. As can be seen from FIG. 33, theperovskite material photovoltaic device produced with BzAI produces agreater current across a range of bias voltages than does the perovskitematerial photovoltaic device produced without BzAI. Additionally, FIG.34 shows box plots for open-circuit voltage (Voc), short-circuit currentdensity (Jsc), Fill Factor (FF) and power conversion efficiency (PCE)for six perovskite material photovoltaic devices produced without BzAI(sample 5, r=reverse scan, f=forward scan, and s=steady-statemeasurement) and six perovskite material photovoltaic devices producedwith BzAI (sample 10). FIG. 35 illustrates external quantum efficiency(EQE) of six perovskite material photovoltaic devices produced withoutBzAI (plot 3505) and six perovskite material photovoltaic devicesproduced with BzAI (plot 3510). Each EQE curve of FIG. 35 has beenintegrated to estimate Jsc in mA/cm², illustrating that the perovskitematerial devices produced with BzAI display a higher Jsc (area under theEQE curve) than the perovskite material devices produced without BzAI.Finally, FIG. 36 shows an admittance spectroscopy plot 3605 forperovskite material photovoltaic devices produced without BzAI and anadmittance spectroscopy plot 3610 for perovskite material photovoltaicdevices produced with BzAI. Admittance spectroscopy plot 3610 showssuppressed ion migration for sample devices including benzylammoniumwhen compared to admittance spectroscopy plot 3605 for sample devicesnot including benzylammonium. Excessive ion migration is known to havedeleterious effects on perovskite material device performance anddurability, indicating that the inclusion of benzylammonium inperovskite material photovoltaic devices may increase device performanceand durability.

Diammonium Butane Cation Enhanced Perovskite

Incorporation of 1,4-diammonium butane, or other poly-ammonium organiccompounds as described below, into the crystal structure of a perovskitematerial may improve the properties of that material. In one embodiment,addition of 1,4-diammonium butane into a FAPbI₃ perovskite as describedbelow may provide the perovskite material with advantageous properties.In some embodiments, 1,4-diammonium butane may be incorporated into aperovskite material utilizing a 1,4-diammonium butane salt in the placeof the bulky organic cation salt in the process described above, and theaddition of the 1,4-diammonium butane salt (or other organicpolyammonium salt described herein) may occur at any stage of theperovskite production method for which addition of the bulky organiccation salt is described above. The inclusion of organic cations, suchas 1,4-diammonium butane, into the crystal structure of a perovskitematerial may result in the formula of the perovskite material deviatingfrom the “ideal” stoichiometry of perovskite materials disclosed herein.For example, inclusion of such organic cations may cause the perovskitematerial to have a formula that is either substoichiometric orsuperstoichiometric with respect to the FAPbI₃ formula. In this case,the general formula for the perovskite material may be expressed asC_(x)M_(y)X_(z), where x, y and z are real numbers.

In one embodiment, a 1,4-diammonium butane salt solution may be added tothe lead halide precursor ink solution prior to deposition. In certainembodiments, a 1,4-diammonium butane salt may be added to the leadhalide precursor ink solution at a concentration of 0.001 mol % to 50mol %. In some embodiments, the 1,4-diammonium butane salt may be addedto the lead halide precursor ink solution at a concentration of 0.1 mol% to 20 mol %. In particular embodiments, the 1,4-diammonium butane saltmay be added to the lead halide precursor ink solution at aconcentration of 1 mol % to 10 mol %.

In another embodiment, 1,4-diammonium butane salt may be added to theformamidinium salt solution prior to contacting the formamidinium saltsolution with the lead halide precursor thin film as described above. Incertain embodiments, a 1,4-diammonium butane salt may be added to theformamidinium iodide salt solution at a concentration of 0.001 mol % to50 mol %. In some embodiments, the 1,4-diammonium butane salt may beadded to the formamidinium iodide salt solution at a concentration of0.1 mol % to 20 mol %. In particular embodiments, the 1,4-diammoniumbutane salt may be added to the formamidinium iodide salt solution at aconcentration of 1 mol % to 10 mol %.

In other embodiments, a 1,4-diammonium butane salt precursor solutionmay be deposited onto a lead halide thin film formed after deposition ofa lead halide precursor ink or onto a perovskite precursor thin filmafter deposition of the formamidinium salt solution. In certainembodiments, the 1,4-diammonium butane salt precursor solution may havea concentration of 0.001 mol % to 50 mol %. In some embodiments, the1,4-diammonium butane salt precursor solution may have a concentrationof 0.1 mol % to 20 mol %. In particular embodiments, the 1,4-diammoniumbutane salt precursor solution may have a concentration of 1 mol % to 10mol %.

An example method for depositing a perovskite material including1,4-diammonium butane includes depositing a lead salt precursor onto asubstrate to form a lead salt thin film and depositing an organic cationsalt precursor comprising a first organic cation salt onto the lead saltthin film to form a perovskite precursor thin film. The lead saltprecursor or the organic cation salt precursor may include a1,4-diammonium butane salt or a 1,4-diammonium butane salt precursor maybe deposited onto the lead salt thin film or the perovskite precursorthin film. Finally the substrate and perovskite precursor thin film maybe annealed to form a perovskite material that includes 1,4-diammoniumbutane. The lead salt precursor and organic cation salt precursor mayinclude any solutions described herein used to produce a perovskite thinfilm.

1,4-diammonium butane has nearly the same length between its ammoniumgroups as occurs between formamidinium cations in the formamidinium leadiodide perovskite material crystal lattice. Accordingly, the1,4-diammonium butane may substitute for two formamidinium ions duringthe formation of an FAPbI₃ material. In alternate embodiments, otheralkyl polyammonium salts may be added to the lead halide precursor inkduring formation of the perovskite material. For example, 1,8 diammoniumoctane, bis(4-aminobutyl)amine, and tris(4-aminobutyl)amine may beadded. Additionally, the polyammonium polycations, including1,4-diammonium butane, may provide the same benefits as the bulkyorganic cations described above by similar mechanisms to those describedabove with respect to the bulky organic cations.

FIG. 13 is a stylized illustration of an effect of addition of a1,4-diammonium butane salt during the process of producing a perovskitematerial may have on the resulting perovskite 7000. As illustrated byFIG. 13, the 1,4-diammonium butane cation 7020 may substitute for twoformamidinium cations 7010 in the perovskite material crystal lattice.In FAPbI₃ perovskite, the spacing between formamidinium cations isapproximately 6.35 Å. The length of the length of the 1,4-diammoniumbutane cation is approximately 6.28 Å, a difference of only 0.07 Å.Accordingly, the 1,4-diammonium butane cation may substitute into theperovskite crystal lattice without significantly changing the propertiesor structure of the perovskite crystal lattice. In some embodiments, theaddition of the 1,4-diammonium butane cation to a perovskite materialmay enhance the properties and stability of the perovskite material. The1,4-diammonium butane cation may act as a rigid structure within theperovskite material, increasing its structural and chemical durability.For example, in some embodiments perovskite material with added1,4-diammonium butane cation may demonstrate superior dry heat stabilitycompared to a perovskite material without 1,4-diammonium butane cation.Additionally, a perovskite material with added 1,4-diammonium butanecation may demonstrate a blue shift in the emission spectra of theperovskite material. In some embodiments the 1,4-diammonium butanecation may be added at a concentration between 0 and 20 mol % to theformamidinium salt solution. In other embodiments the 1,4-diammoniumbutane cation may be added at a concentration between 1 and 5 mol % tothe formamidinium salt solution. In a particular embodiment the1,4-diammonium butane cation added at a concentration 5 mol % to theformamidinium salt solution.

Experimental evidence has shown that for additions of up to 20%1,4-diammonium butane to a perovskite material, the lattice parametersdo not appreciably shift. FIG. 14 provides x-ray diffraction peaks (XRD)for perovskite having 0 mol %, 5 mol %, 10 mol %, and 20 mol %1,4-diammonium butane iodide (“DABI”). For each concentration the majorpeaks occur at the same points, indicating that the lattice parametersfor a perovskite material do not change appreciably with addition of aconcentration between 0 mol % and 20 mol % 1,4-diammonium butane. Theaddition of 1,4-diammonium butane may create small intensitydiffractions at less than 13° 2θ with Cu-Kα radiation, which areindicative of a small amount of 2D or layered perovskite phase.

FIG. 15 provides images of perovskite samples having 0 mol %, 1 mol %,2.5 mol % and 5 mol % exposed to a temperature of 85° C. at 0% relativehumidity for seven days. The perovskite material with 0 mol % DABI showssignificant lightening in color after one day and even more significantyellowing after seven days. This indicates that the perovskite materialwith 0 mol % DABI has degraded significantly after one day exposed tothe testing conditions. The perovskite material samples with 1 mol %,2.5 mol % and 5 mol % all remain dark after seven days, indicating thataddition of as little as 1 mol % DABI significantly increases so called“dry heat” stability of the perovskite material.

Additionally, addition of 1,4-diammonium butane to a perovskite materialmay result in a slight blue shift of photoluminescence seen from aperovskite material when compared to a perovskite material without1,4-diammonium butane. This blue shift results from the passivation oftrap states within the perovskite material resulting from the additionof 1,4-diammonium butane. This blue shift indicates that the addition of1,4-diammonium butane to a perovskite material decreases defect densityin the perovskite material crystal lattice without changing the crystalstructure of the perovskite material. For example, it has been observedthat the resulting blue shift seen in an FAPbI₃ perovskite material with20 mol % of added 1,4-diammonium butane compared to a FAPbI₃ perovskitematerial without 1,4-diammonium butane is a change of 0.014 eV, from1.538 eV with no 1,4-diammonium butane to 1.552 eV with 20 mol %1,4-diammonium butane.

In other embodiments, other ammonium complexes may be added duringformation of the perovskite material. For example, FIG. 16 illustratesthree ammonium compounds, 1,8-diammonium octane,bis(4-aminobutyl)-ammonium and tris(4-aminobutyl)-ammonium, which may beadded to a perovskite material in the same method as described abovewith respect to the 1,4-diammonium butane cation. 1,8-diammonium octanemay occupy the space of two formamidinium cations (“A-sites”) of aFAPbI₃ perovskite material crystal lattice when introduced during theformation of the perovskite material as described above.Bis(4-aminobutyl)-ammonium may occupy the space of three A-sites of aFAPbI₃ perovskite material crystal lattice when introduced during theformation of the perovskite material as described above.Tris(4-aminobutyl)-ammonium may occupy the space of four A-sites of aFAPbI₃ perovskite material crystal lattice when introduced during theformation of the perovskite material as described above. FIGS. 16A-Cprovides a stylized illustration of an incorporation into FAPbI₃perovskite material crystal lattice of the three ammonium compoundsillustrated in FIG. 16. FIG. 16A is a stylized illustrationincorporation of 1,8-diammonium octane into a FAPbI₃ perovskite materialcrystal lattice 7100. As illustrated by FIG. 16A, the 1,8-diammoniumoctane cation 7120 may substitute for two formamidinium cations 7110 inthe perovskite material crystal lattice. FIG. 16B is a stylizedillustration incorporation of bis(4-aminobutyl)-ammonium into a FAPbI₃perovskite material crystal lattice 7200. As illustrated by FIG. 16B,the bis(4-aminobutyl)-ammonium cation 7220 may substitute for threeformamidinium cations 7210 in the perovskite material crystal lattice.FIG. 16C is a stylized illustration incorporation oftris(4-aminobutyl)-ammonium into a FAPbI₃ perovskite material crystallattice 7300. As illustrated by FIG. 16c , thetris(4-aminobutyl)-ammonium cation 7320 may substitute for fourformamidinium cations 7310 in the perovskite material crystal lattice.In other embodiments, alkyl diammonium complexes with carbon chainsbetween 2 and 20 carbon atoms may be added to a perovskite material. Insome embodiments, a combination of ammonium complexes may be added to aperovskite material.

Cross-Linked Interfacial Layers

In some embodiments, a PV device may include one or more cross-linkedinterfacial layers. Cross-linked interfacial layers may be physicallyand chemically more robust than non-cross-linked interfacial layers. Forexample, cross-linked interfacial layers may be harder, tougher, denser,less permeable to liquids and/or gases, and less reactive thaninterfacial layers that are not cross linked. Additionally, cross-linkedinterfacial layers may have different electrical properties thaninterfacial layers that are not cross-linked. Crosslinked interfaciallayers may include dielectric polymers, crosslinked polymers,crosslinked fullerenes, and composites with fullerenes andnanoparticles. In particular embodiments, crosslinked interfacial layersmay be deposited as an IFL between a photoactive layer an electrode,such as IFL 1030 and IFL 1050 of FIG. 1.

Cross linked interfacial layers may include one or more of polymers andfullerene and fullerene derivatives.

Examples of polymers include:

Polyvinylarenes including ortho, para, or meta isomers and the di, tri,tetra, and penta-substituted derivatives such as: Polystyrene,Polyvinylnapthalenes, Polyvinylphenols (e.g. Poly(4-vinylphenol),Polyvinylanilines, Polyvinylbenzoic acid, Polyvinylhaloarenes (e.g.Poly(4-chlorostyrene)), Polyvinylpyridine (e.g. Poly(4-vinylpyridine)),Polyvinylthiophene, Polyvinylpyrrole, Polyvinylfuran, andPolyvinylpyrrolidone.

Polyarenes including, Polyacenaphthylene, Polyphenylene oxides,Polyphenylene Sulfides, Polyanilines, Polyfuran, Polythiophene, andPolypyrroles.

Polyvinylalkanes including, Polyolefins (e.g. Polyethylene,Polypropylene, Polyacetylene), Polyvinylalcohols, Polyvinylacetate,Polyvinylhalides, Polyacrylic acid, Polymethacrylate,Polymethylmethacrylate, Polyacrylonitrile, Polyvinylcyclohexane,Polyvinylamines, and Polyvinylthiols.

Examples of fullerenes include: C₆₀, C₇₀ and C₈₄, as well as:

Substituted fullerenes including: Azafullerenes (C_(60-n)n_(n)),Borafullerenes (C_(60-n)B_(n)), Azaborafullerenes(C_(60-(n+m))N_(n)B_(m)).

Endohedral fullerenes (endofullerenes) including Metallofullerenes(M@C₆₀ where M is any transition metal), Trimetasphere carbonnanomaterials (M₃N@C₈₀ where M is any lanthanide or transition metal),and M₂@C₈₀ where M is any transition metal; and Non-Metal DopedFullerenes (e.g. Ng@C₆₀ where Ng═He, Ne, Ar, Kr, Xe (noble gases) andH₂@C₆₀)

Exohedral Fullerenes (exofullerences) including Fullerenols (e.g.C₆₀(OH)_(n) where n=1 to 60), Alkylfullerenes (e.g. C₆₀R_(n) where n=1to 60), Halofullerenes: (e.g. C₆₀X_(n) where X═F, Cl, Br, or I and n=1to 60), Hydrofullerenes: (e.g. C₆₀H_(n) where n=1 to 60),Methanofullerene derivatives (e.g. Bingel Derivatives includingDialkylestermethanofullerenes: (C₆₀C(CO₂R)₂ where R=an alkyl or arylgroup), Dialkynylmethanofullerenes (C₆₀C(C₂R)₂) Fullerenedihydrophyrroles (C₆₀CR₂NCCO₂R); Prato Derivatives: C₆₀C₂NR where R=analkyl or aryl group Phenyl-C₆₁-butyric acid methyl ester (PCMA),Phenyl-C₆₁-butyric acid methyl ester (PCMB)), Transition Metal FullereneComplexes, and Fulleriod (methanoannulenes) (Ring opened fullerenederivatives).

In one embodiment, a cross-linked interfacial layer may be composed offullerenes cross-linked by one or more polymers. Crosslinked polymersmay include polystyrene, [6,6]-phenyl-C61-butyric acid methyl ester(PCBM); poly(4-vinylphenol); [6,6]-phenyl-C61-butyric acid (PCBA) orother poly(3-vinylphenol), poly(2-vinylphenol),poly(3,5-dihydroxystyrene), poly(3,4-dihydroxystyrene), andpoly(3,4,5-trihydroxystyrene) be substituted in place ofpoly(4-vinylphenol), polyvinylaryls.

In one embodiment, a crosslinked interfacial layer may comprise amixture of polystyrene and a silane monomer. As described herein, asilane may include any hydro-, hydroxy-, halo-, alkyl-, alkenyl-,alkynyl-, cyclo-, aromatic-, alkoxylalkyl-, alkoxyalkeny-,alkoxyaromatic-, haloalkyl-, haloalkenyl-, haloalkynl-, andhaloaromatic-silane. In other embodiments, boranes, amines, phosphines,dicarboxylic acids, disulfide linkages, and cyclophane and cyclophanederivatives may be utilized in crosslinking IFLs in place of silanes.FIG. 37 illustrates a structure of a crosslinked interfacial layer madeup of polystyrene and a halosilylalkane before and after crosslinking.In the embodiment illustrated in FIG. 37, 1,6-bis-(trichlorosilyl)hexaneacts to crosslink polystyrene polymer molecules in the interfaciallayer. However, in other embodiments, any alkane or arene (e.g. benzene)may be substituted for the illustrated hexane and any halogen or alkoxygroup (e.g. methoxy, ethoxy) may be substituted for the chloro groups.

In another embodiment, a crosslinked interfacial layer may comprise amixture of polystyrene, a silane, and [6,6]-phenyl-C61-butyric acidmethyl ester (PCBM). In other embodiments, boranes, amines, phosphines,dicarboxylic acids, disulfide linkages, and cyclophane and cyclophanederivatives may be utilized in crosslinking IFLs in place of silanes.FIG. 38 illustrates a structure of a crosslinked interfacial layer madeup of PCBM, polystyrene, and a halosilylalkane before and aftercrosslinking. FIG. 38 illustrates the alkyl silane acting to crosslinkpolystyrene polymer molecules in the interfacial layer, whileimmobilizing the PCBM molecules within the crosslinked polymerinterfacial layer.

In one embodiment, a crosslinked interfacial layer may comprise amixture of poly(4-vinylphenol) and a silane monomer. In otherembodiments, boranes, amines, phosphines, dicarboxylic acids, disulfidelinkages, and cyclophane and cyclophane derivatives may be utilized incrosslinking IFLs in place of silanes. In other embodiments,poly(3-vinylphenol), poly(2-vinylphenol), poly(3,5-dihydroxystyrene),poly(3,4-dihydroxystyrene), and poly(3,4,5-trihydroxystyrene) besubstituted in place of poly(4-vinylphenol). FIG. 39 illustrates astructure of a crosslinked interfacial layer made up ofpoly(4-vinylphenol) and a halosilylalkane before and after crosslinking.FIG. 39 illustrates the halosilylalkane acting to crosslinkpoly(4-vinylphenol) polymer molecules in the interfacial layer.

In another embodiment, a crosslinked interfacial layer may comprise amixture of poly(4-vinylphenol), a silane, and PCBM. In otherembodiments, boranes, amines, phosphines, dicarboxylic acids, disulfidelinkages, and cyclophane and cyclophane derivatives may be utilized incrosslinking IFLs in place of silanes. In other embodiments,poly(3-vinylphenol), poly(2-vinylphenol), poly(3,5-dihydroxystyrene),poly(3,4-dihydroxystyrene), and poly(3,4,5-trihydroxystyrene) besubstituted in place of poly(4-vinylphenol). FIG. 40 illustrates astructure of a crosslinked interfacial layer made up of PCBM,poly(4-vinylphenol), and a halosilylalkane before and aftercrosslinking. FIG. 40 illustrates the halosilylalkane acting tocrosslink poly(4-vinylphenol) polymer molecules in the interfaciallayer, while immobilizing the PCBM molecules within the crosslinkedpolymer interfacial layer.

In another embodiment, a crosslinked interfacial layer may comprise amixture of polystyrene, a silane, and [6,6]-phenyl-C61-butyric acid(PCBA). In other embodiments, boranes, amines, phosphines, dicarboxylicacids, disulfide linkages, and cyclophane and cyclophane derivatives maybe utilized in crosslinking IFLs in place of silanes. FIG. 41illustrates a structure of a crosslinked interfacial layer made up ofPCBA, polystyrene, and a halosilylalkane before and after crosslinking.FIG. 41 illustrates the halosilylalkane acting to crosslink polystyrenepolymer molecules and PCBA molecules in the interfacial layer.

In another embodiment, a crosslinked interfacial layer may comprise amixture of poly(4-vinylphenol), a silane, and PCBA. In otherembodiments, boranes, amines, phosphines, dicarboxylic acids, disulfidelinkages, and cyclophane and cyclophane derivatives may be utilized incrosslinking IFLs in place of silanes. In other embodiments,poly(3-vinylphenol), poly(2-vinylphenol), poly(3,5-dihydroxystyrene),poly(3,4-dihydroxystyrene), and poly(3,4,5-trihydroxystyrene) besubstituted in place of poly(4-vinylphenol). FIG. 42 illustrates astructure of a crosslinked interfacial layer made up of PCBA,poly(4-vinylphenol), and a halosilylalkane before and aftercrosslinking. FIG. 42 illustrates the halosilylalkane acting tocrosslink poly(4-vinylphenol) polymer molecules and PCBA molecules inthe interfacial layer. As illustrated in FIG. 42 the PCBA molecules arefully immobilized within the crosslinked polymer interfacial layer bybonding to the silane groups of the halosilylalkane compound.

A method for depositing a cross-linked fullerene interfacial layer isdescribed below. First cyclophane is converted to a dimethylbenzeneradical. Next the dimethyl benzene radical is deposited on to asubstrate along with fullerenes, resulting in a cross-linked interfaciallayer with fullerenes cross-linked by one or more dimethylbenzenemolecules. In certain embodiments, the fullerenes and the dimethylbenzene radical may be deposited by chemical vapor deposition,evaporation, or plasma deposition. If deposited onto a perovskite layer,the interfacial layer deposited by this method may form a conformalcoating along the surface of the perovskite material. The fullerenes andcross-linking dimethyl benzene polymer may fill in irregulates in thesurface of the perovskite, thereby enhancing the degree of contactbetween the interfacial layer and the perovskite layer.

An alternative method for depositing a cross-linked fullereneinterfacial layer is described below. First fullerenes arefunctionalized to an alkyl hydroxide group to the surface of thefullerenes. Next, the functionalized fullerenes are deposited onto asubstrate. In certain embodiments the functionalized fullerenes may bedeposited onto a perovskite layer of a photovoltaic device. Thefunctionalized fullerenes may be deposited by methods including but notlimited to spin coating, slot-die printing, chemical vapor deposition,thermal evaporation, sputtering, atomic layer deposition, extrusion, andgravure printing. Next, the fullerene coating may be treated with asilane compound to form a cross-linked silicon-fullerene interfaciallayer. The silane compound may include any hydro-, hydroxy-, halo-,alkyl-, alkenyl-, alkynyl-, cyclo-, aromatic-, alkoxylalkyl-,alkoxyalkeny-, alkoxyaromatic-, haloalkyl-, haloalkenyl-, haloalkynl-,and haloaromatic-silane. In other embodiments, boranes, amines,phosphines, dicarboxylic acids, disulfide linkages, and cyclophane andcyclophane derivatives may be utilized in crosslinking IFLs in place ofsilanes. In some embodiments, the silane compound may be ahalosilylalkane. The halosilyalkane may be1,6-bis(trichlorosilyl)hexane, in particular embodiments. Such asilicon-fullerene cross-linked interfacial layer may have theadvantageous electrical properties of fullerenes enhanced by thephysical properties of a silicone. For example, the silicon-fullereneinterfacial layer may be water resistant and flexible while maintainingthe desirable electrical properties of fullerenes.

Yet another method for depositing a cross-linked fullerene interfaciallayer is described below. First, a polymer is dissolved into a solventto form a polymer solution. In certain embodiments, the solvent used todissolve the polymer may include alcohols, aryl solvents, chlorinatedsolvents, ketones, nitriles, alkane solvents, formamides, esters, andcombinations thereof. The concentration of the polymer in the solutionmay range from about 1 uM to about 1M. In some embodiments, theconcentration of the polymer in the solution may range from about 1 mMto about 10 M. A fullerene is then added to the polymer solution. Incertain embodiments, the fullerene may be added directly as a solid intothe polymer solution or first dissolved in a solvent (e.g., benzene,chlorobenzene, dichlorobenzene, toluene, chloroform) and then added tothe polymer solution. In certain embodiments, the fullereneconcentration after addition may range from about 1 uM to about 10M. Insome embodiments, the fullerene concentration in the solution may rangefrom about 1 mM to about 1 M. A crosslinker is then added to the polymersolution either directly as a liquid or solid. In certain embodiments, acrosslinker may be dissolved in a solvent and then added to the polymersolution. The solvent used to dissolve the crosslinker may includealcohols, aryl solvents, chlorinated solvents, acetone, acetonitrile,alkyl solvents, formamides, esters, and combination thereof. In someembodiments, the crosslinker may be added to the polymer solution priorto the addition of the fullerene. The crosslinker concentration afteraddition to the fullerene and polymer solution may range from about 1 uMto about 10M. In some embodiments, the crosslinker concentration in thesolution may range from about 1 mM to about 1 M. In certain embodiments,this solution may be prepared in a substantially air-free (i.e., nooxygen or water) environment, which may avoid premature crosslinking andsolidification of the cross-linked interfacial layer ink. In certainembodiments, the crosslinker may be added immediately before theapplication of the cross-linked interfacial layer ink. The polymerdescribed herein may include any polymers disclosed in the presentdisclosure and the fullerene may include any fullerene or fullerenederivative disclosed in the present disclosure. Alternatively, a polymermay be added to a fullerene and/or crosslinker solution, as describedabove.

The cross-linked interfacial layer ink of the present disclosure may bedeposited by blade coating, spin-coating, slot-die printing, ink-jetprinting, gravure printing, screen printing, sputtering, spray coating,drop casting, or any other solution-based deposition technique describedin the present disclosure. In certain embodiments, the deposition mayoccur in ambient atmosphere, a controlled atmosphere, and/or anatmosphere substantially free of water, carbon dioxide, and oxygen. Thewet layer may be allowed to dry in the ambient or may be allowed to dryat elevated temperature (e.g., 0 to 250° C.). The wet or dry layer bemay exposed to UV radiation to promote crosslinking. In certainembodiments, a crosslinker may require UV irradiation to crosslink.

The crosslinked interfacial layer may be deposited directly on theperovskite material layer, onto a layer previously deposited on theperovskite layer (e.g., fullerenes, dielectric materials, semiconductingmaterials, any interfacial layer described in the present disclosure),or onto a conductive substrate of the present disclosure. When thecrosslinked interfacial layer is deposited onto the conductivesubstrate, a perovskite material may be deposited directly onto thecrosslinked interfacial layer, or one or more additional interfaciallayers may be deposited on the crosslinked interfacial layer before theperovskite material is deposited by any technique described herein.

In other embodiments, various different fullerenes, polymers, andcross-linking agents may be utilized in place of those already describedabove. For example, FIG. 43 illustrates an example withpolyhydroxylfullerene as a fullerene, FIG. 44 illustrates an examplewith formaldehyde as the cross-linking agent, and FIG. 45 illustrates anexample with poly(4-chlorostyrene) as the polymer and sodium sulfide asthe cross-linking agent.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of the present invention. In particular, every range of values(of the form, “from about a to about b,” or, equivalently, “fromapproximately a to b,” or, equivalently, “from approximately a-b”)disclosed herein is to be understood as referring to the power set (theset of all subsets) of the respective range of values, and set forthevery range encompassed within the broader range of values. Also, theterms in the claims have their plain, ordinary meaning unless otherwiseexplicitly and clearly defined by the patentee.

The invention claimed is:
 1. A cross-linked interfacial layercomposition comprising: a fullerene or fullerene derivative; across-linking agent, wherein the cross-linking agent comprises a silane,wherein the silane is a halosilyalkane; and one or more polymers.
 2. Thecross-linked interfacial layer composition of claim 1, wherein thefullerene or fullerene derivative is selected from the group consistingof: a generic fullerene, a substituted fullerene, an endohedralfullerene, an exohedral fullerene, and any combination thereof.
 3. Thecross-linked interfacial flayer composition of claim 1, wherein thefullerene or fullerene derivative is selected from the group consistingof: [6,6]-phenyl-C61-butyric acid methyl ester, [6,6]-phenyl-C61-butyricacid, polyhydroxylfullerene, and any combination thereof.
 4. Thecross-linked interfacial layer composition of claim 1, wherein the oneor more polymers comprise a polyvinylaryl.
 5. The cross-linkedinterfacial layer composition of claim 1, wherein the one or morepolymers are selected from the group consisting of: 4-(polyvinylphenol),poly(3-vinylphenol), poly(2-vinylphenol), poly(3,5-dihydroxystyrene),poly(3,4-dihydroxystyrene), poly(3,4,5-trihydroxystyrene),poly(4-chlorostyrene), and any combination thereof.
 6. The cross-linkedinterfacial layer composition of claim 1, wherein the one or morepolymers are selected from the group consisting of: polystyrene,polyvinylnapthalenes, polyvinylphenols, polyvinylanilines,polyvinylbenzoic acid, polyvinylhaloarenes, polyvinylpyridine,polyvinylthiophene, polyvinylpyrrole, polyvinylfuran,polyvinylpyrrolidone, and any combination thereof.
 7. The cross-linkedinterfacial layer composition of claim 1, wherein the one or morepolymers are selected from the group consisting of: polyacenaphthylene,polyphenylene oxides, polyphenylene sulfides, polyanilines, polyfuran,polythiophene, polypyrroles, and any combination thereof.
 8. Thecross-linked interfacial layer composition of claim 1, wherein the oneor more polymers are selected from the group consisting of: polyolefins,polyvinylalcohols, polyvinylacetate, polyvinylhalides, polyacrylic acid,polymethacrylate, polymethylmethacrylate, polyacrylonitrile,polyvinylcyclohexane, polyvinylamines, polyvinylthiols, and anycombination thereof.
 9. A photovoltaic device comprising: a photoactivematerial comprising a perovskite material; and an interfacial layercomprising a cross-linked polymer comprising: a fullerene or fullerenederivative; a cross-linking agent; and one or more polymers.
 10. Thephotovoltaic device of claim 9, wherein the fullerene or fullerenederivative is selected from the group consisting of:[6,6]-phenyl-C61-butyric acid methyl ester, [6,6]-phenyl-C61-butyricacid, polyhydroxylfullerene, and any combination thereof.
 11. Thephotovoltaic device of claim 9, wherein the fullerene or fullerenederivative is selected from the group consisting of: a genericfullerene, a substituted fullerene, an endohedral fullerene, anexohedral fullerene, and any combination thereof.
 12. The photovoltaicdevice of claim 9, wherein the cross-linking agent comprises a silane.13. The photovoltaic device of claim 12, wherein the silane is ahalosilyalkane.
 14. The photovoltaic device of claim 9, wherein the oneor more polymers comprise a polyvinylaryl.
 15. The photovoltaic deviceof claim 9, wherein the one or more polymers are selected from the groupconsisting of: 4-(polyvinylphenol), poly(3-vinylphenol),poly(2-vinylphenol), poly(3,5-dihydroxystyrene),poly(3,4-dihydroxystyrene), poly(3,4,5-trihydroxystyrene),poly(4-chlorostyrene), and any combination thereof.
 16. The photovoltaicdevice of claim 9, wherein the one or more polymers are selected fromthe group consisting of: polystyrene, polyvinylnapthalenes,polyvinylphenols, polyvinylanilines, polyvinylbenzoic acid,polyvinylhaloarenes, polyvinylpyridine, polyvinylthiophene,polyvinylpyrrole, polyvinylfuran, polyvinylpyrrolidone, and anycombination thereof.
 17. The photovoltaic device of claim 9, wherein theone or more polymers are selected from the group consisting of:polyacenaphthylene, polyphenylene oxides, polyphenylene sulfides,polyanilines, polyfuran, polythiophene, polypyrroles, and anycombination thereof.
 18. The photovoltaic device of claim 9, wherein theone or more polymers are selected from the group consisting of:polyolefins, polyvinylalcohols, polyvinylacetate, polyvinylhalides,polyacrylic acid, polymethacrylate, polymethylmethacrylate,polyacrylonitrile, polyvinylcyclohexane, polyvinylamines,polyvinylthiols, and any combination thereof.